Unmount unusable partition instead of putting device into crashloop.

Bug: 233902887
Test: presubmit
Change-Id: I91963f4fcde27656e1a253d6181e4d81b02b26fe
Merged-In: I91963f4fcde27656e1a253d6181e4d81b02b26fe
(cherry picked from commit 335f4714bb369932c056d9aa89071943d0488b69)
1 file changed