Set uninstall button to gray color.

For user installed app, set the uninstall button as negative button so
that it will have the correct color.

Change-Id: Ic631386affddf82ae0ebbf29fb572de1f067fc90
Fixes: 68154647
Test: make RunSettingsRoboTests

src/com/android/settings/applications/InstalledAppDetails.java

@@ -348,7 +348,7 @@ public class InstalledAppDetails extends AppInfoBase
             enabled = false;
             mActionButtons.setButton1Visible(false);
         }
-        mActionButtons.setButton1Text(R.string.uninstall_text);
+        mActionButtons.setButton1Text(R.string.uninstall_text).setButton1Positive(false);
         return enabled;
     }