Guardrail for pull cooldown/timeout

Enforce a 1 second minimum cooldown and a 10 second maximum timeout on
pullers.

Test: bit statsd_test:*
Test: atest LibStatsPullTests
Test: atest GtsStatsdHostTestCases
Bug: 152543610
Change-Id: Ida0047235a7e56d7b700f1a7ab5cfbc2a147caeb