Allow some time for recording in testVideoSnapshot

- Stagefright design is to return an error if it hasn't received sufficient
encoded frames when stop is called.  Sometimes, the calls in testVideoSnapshot
go faster than the startTimeOffsetUs resulting in no frames captured and
a failed test case.
- The sleep is added in consistent to other media recording test cases.

Change-Id: Ic15518a47ff04a886c0c51974b53b8b8e1081b09
1 file changed