Add recovery_host_test to TEST_MAPPING.

Also remove the AndroidTest.xml file, which is no longer needed (the
`data` property in Android.bp takes care of that). The AndroidTest.xml
file would otherwise block `atest recovery_host_test` from running.

Test: TreeHugger; check the test result.
Change-Id: If545878a1f3ae627986e19a94b42162f133b9098