Fix CDM discovery timeout

CDM has a regression preventing activity launches after timeout
due to DiscoveryState potentially remaining in FINISHED_TIMEOUT.
We must ensure activities are cancelled when timeout occurs while discovery is in progress.

Flag: EXEMPT bugfix
Bug: 342470917
Bug: 353187081
Test: CTS
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:98cbbae537632142d0b53c290014268c365de2c0)
Merged-In: I531676195e674e2ce52632e5bae6c93fc1d5e1d0
Change-Id: I531676195e674e2ce52632e5bae6c93fc1d5e1d0