Change perf tests to have less deviation.

Simultaneous writes might get in a way of testing.

BEFORE:
[1/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_badRTC: PASSED (36.482s)
	testPersistedJobReading_fewJobs_badRTC_mean: 10263642
	testPersistedJobReading_fewJobs_badRTC_mean: 10498465
	testPersistedJobReading_fewJobs_badRTC_mean: 10773303
	testPersistedJobReading_fewJobs_badRTC_mean: 10134928
	testPersistedJobReading_fewJobs_badRTC_mean: 10781215
[2/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_manyJobs: PASSED (38.200s)
	testPersistedJobWriting_manyJobs_mean: 37482702
	testPersistedJobWriting_manyJobs_mean: 60457027
	testPersistedJobWriting_manyJobs_mean: 36667759
	testPersistedJobWriting_manyJobs_mean: 36411327
	testPersistedJobWriting_manyJobs_mean: 36966431
[3/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_goodRTC: PASSED (38.297s)
	testPersistedJobReading_manyJobs_goodRTC_mean: 43782739
	testPersistedJobReading_manyJobs_goodRTC_mean: 44142442
	testPersistedJobReading_manyJobs_goodRTC_mean: 43433056
	testPersistedJobReading_manyJobs_goodRTC_mean: 43435353
	testPersistedJobReading_manyJobs_goodRTC_mean: 43571135
[4/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_fewJobs: PASSED (36.485s)
	testPersistedJobWriting_fewJobs_mean: 9229892
	testPersistedJobWriting_fewJobs_mean: 9100376
	testPersistedJobWriting_fewJobs_mean: 8941938
	testPersistedJobWriting_fewJobs_mean: 8922329
	testPersistedJobWriting_fewJobs_mean: 8929850
[5/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_goodRTC: PASSED (36.533s)
	testPersistedJobReading_fewJobs_goodRTC_mean: 10774626
	testPersistedJobReading_fewJobs_goodRTC_mean: 10629069
	testPersistedJobReading_fewJobs_goodRTC_mean: 10166131
	testPersistedJobReading_fewJobs_goodRTC_mean: 10435772
	testPersistedJobReading_fewJobs_goodRTC_mean: 10990735
[6/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_badRTC: PASSED (38.883s)
	testPersistedJobReading_manyJobs_badRTC_mean: 88288009
	testPersistedJobReading_manyJobs_badRTC_mean: 43032098
	testPersistedJobReading_manyJobs_badRTC_mean: 86609764
	testPersistedJobReading_manyJobs_badRTC_mean: 42699765
	testPersistedJobReading_manyJobs_badRTC_mean: 86939196

AFTER:
com.android.frameworks.perftests.job (6 Tests)
[1/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_badRTC: PASSED (20.018s)
	testPersistedJobReading_fewJobs_badRTC_mean: 4403782
	testPersistedJobReading_fewJobs_badRTC_mean: 4329086
	testPersistedJobReading_fewJobs_badRTC_mean: 4361577
[2/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_manyJobs: PASSED (20.894s)
	testPersistedJobWriting_manyJobs_mean: 33269431
	testPersistedJobWriting_manyJobs_mean: 32886187
	testPersistedJobWriting_manyJobs_mean: 33093695
[3/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_goodRTC: PASSED (20.822s)
	testPersistedJobReading_manyJobs_goodRTC_mean: 39305058
	testPersistedJobReading_manyJobs_goodRTC_mean: 38768541
	testPersistedJobReading_manyJobs_goodRTC_mean: 38944530
[4/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_fewJobs: PASSED (21.046s)
	testPersistedJobWriting_fewJobs_mean: 4301181
	testPersistedJobWriting_fewJobs_mean: 4164938
	testPersistedJobWriting_fewJobs_mean: 4146446
[5/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_goodRTC: PASSED (21.137s)
	testPersistedJobReading_fewJobs_goodRTC_mean: 4230574
	testPersistedJobReading_fewJobs_goodRTC_mean: 4184341
	testPersistedJobReading_fewJobs_goodRTC_mean: 4192015
[6/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_badRTC: PASSED (21.016s)
	testPersistedJobReading_manyJobs_badRTC_mean: 39166861
	testPersistedJobReading_manyJobs_badRTC_mean: 39049685
	testPersistedJobReading_manyJobs_badRTC_mean: 38929124

Bug: 135200955
Test: atest JobStoreTest CtsJobSchedulerTestCases JobStorePerfTests

Change-Id: I9e69ded28bed13834ba82a5d74283711422c5124