Add MicrodroidHostTestCases to TEST_MAPPING

Microdroid shares init with its host, defined under system/core/init.
This change adds MicrodroidHostTestCases to TEST_MAPPING to ensure that
Microdroid tests can verify patches to init.

Test: presubmit
Change-Id: I55f7e3ffbaf3401d145afac5f7c53d83f69e6ba7
1 file changed