Address timing issues in ConnectivityConstraintTest

The test failed to account for a gap between WiFi being connected
and Mobile being connected.

Also, in my experiments reconnecting to WiFi sometimes took longer
than 30 seconds, so I increased the timeout to 60 seconds.

Bug: 138253466
Test: repeatedly run "atest android.jobscheduler.cts.ConnectivityConstraintTest"

Change-Id: Iaf22bff7d0818693b0a09944dc19d760e1c46c4c