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
diff --git a/TEST_MAPPING b/TEST_MAPPING
index a7c34dd..c87ece2 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -8,6 +8,10 @@
     },
     {
       "name": "recovery_component_test"
+    },
+    {
+      "name": "recovery_host_test",
+      "host": true
     }
   ]
 }