Poll for external storage directory mounted before starting test.

FuseDaemonHostTest device test might start right after device is
booted, this makes test start I/O operation before external storage
directory is mounted. Poll for externalStorageMountState to change
to MEDIA_MOUNTED before starting the test.

Test: atest FuseDaemonHostTest
Bug: 149132662
Change-Id: I4499131fb80a91997ef412936179d3036a509ca8
4 files changed