Attempt to improve test robustness.

We've seen evidence that some shell commands are exiting early
before they've finished.  This change attempts to retry a failed
shell command a few times before actually giving up.

Bug: 158445038
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: I1729724f21e15cdd5dec4c32009a76003484de1d
1 file changed