Reconcile Zygote process name code with Q release.

Some Zygote code that was pushed to AOSP master is different from the
pushed Q release. In particular, a call to set the process name for a
Zygote child was missing, causing an app zygote test to fail.

Bug: 139535125
Test: atest android.app.cts.ServiceTest#testAppZygoteServices
Change-Id: I53b0bc0116f1573cb1e52a998e10346bd5601f67
Merged-In: I2bce277ff8f2de4614e19d5385fe6712b076f9c9