Execute explicit health check mitigation immediately

Explicit health check failures are given priority over
general app crashes (which requires thresholding of a
number of failures). Give explicit health check failures
priority, similar to how native crashes are handled.

Test: atest StagedRollbackTest
Bug: 145584672
Change-Id: I9dd736a67431e1a9f762dd6fed13f0e3c9ee8ee4