Add @FlakyTest annotation to LegacyProviderMigrationTest

These tests are flaky because they reset vold, which now has to mount
all volumes. Tests remain flaky even if we poll for 30 seconds to see
externalStorageState=MEDIA_MOUNTED. Hence, adding @FlakyTest annotation
to indicate that the test can be flaky.

Bug: 176977253
Test: Presubmit.
Change-Id: I9a47c4928d18bfe33cd7f181bd4942e45720d7d5
Merged-In: I9a47c4928d18bfe33cd7f181bd4942e45720d7d5
(cherry picked from commit 3429c3354b1788639b374b5d19c1cc05d7a4d589)
1 file changed