Skip testInstall(Multiple)StagedApk if the user is not system user

- testInstallStagedApk and testInstallMultipleStagedApk work
only if the user is system user.

Bug: 134093258
Test: Run CtsStagedInstallHostTestCases
Change-Id: I81d17399865c24c70e421282616e3ab8664dd071
diff --git a/hostsidetests/stagedinstall/src/com/android/tests/stagedinstall/host/StagedInstallTest.java b/hostsidetests/stagedinstall/src/com/android/tests/stagedinstall/host/StagedInstallTest.java
index 41ad7ee..4ad9927 100644
--- a/hostsidetests/stagedinstall/src/com/android/tests/stagedinstall/host/StagedInstallTest.java
+++ b/hostsidetests/stagedinstall/src/com/android/tests/stagedinstall/host/StagedInstallTest.java
@@ -77,6 +77,7 @@
      */
     @Test
     public void testInstallStagedApk() throws Exception {
+        assumeSystemUser();
         runPhase("testInstallStagedApk_Commit");
         getDevice().reboot();
         runPhase("testInstallStagedApk_VerifyPostReboot");
@@ -117,11 +118,18 @@
 
     @Test
     public void testInstallMultipleStagedApks() throws Exception {
+        assumeSystemUser();
         runPhase("testInstallMultipleStagedApks_Commit");
         getDevice().reboot();
         runPhase("testInstallMultipleStagedApks_VerifyPostReboot");
     }
 
+    private void assumeSystemUser() throws Exception {
+        String systemUser = "0";
+        assumeThat("Current user is not system user",
+                getDevice().executeShellCommand("am get-current-user").trim(), equalTo(systemUser));
+    }
+
     @Test
     public void testGetActiveStagedSession() throws Exception {
         runPhase("testGetActiveStagedSession");