Add StagedInstallInternalTest to adb TEST_MAPPING file

StagedInstallInternalTests contains test that verify staged installation
using adb commandline (e.g `adb install`) is working correctly.

Bug: 158314277
Test: atest --test-mapping system/core
Change-Id: Icc3bd464a91f31095316fbb85941e5e03089aaad
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 7933629..dff6407 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -58,5 +58,10 @@
     {
       "name": "propertyinfoserializer_tests"
     }
+  ],
+  "imports": [
+    {
+      "path": "frameworks/base/tests/StagedInstallTest"
+    }
   ]
 }