Reset health check duration to default during testing

Since other tests may set watchdog_request_timeout_millis to
different values, this test may be flaky if tests do not
clean up properly. Set up the appropriate DeviceConfig value
during setup to avoid this.

Test: atest ExplicitHealthCheckServiceImplTest
Bug: 148144156
Exempt-From-Owner-Approval: Owner delegated to another reviewer
Change-Id: I552ed2bfdc9be6fafdeea0567ec90532da68715e
1 file changed