test: process APP_NAME when deciding what apps to disable

When running acceptance tests, we disable the firstrunwizard
and notifications app by default. These apps are often provided
in a bundled ownCloud core tarball. But they can get in the way
of webUI tests, because:

- the firstrunwizard might display itself at the very start of testing
- notifications can appear at the top of the webUI, and might obscure
  things that are being tested.

But if we are actually testing one of these apps, then we don't want
to disable the app.

The logic in acceptance ytetst run.sh is enhanced to avoid disabling
the app when it is the app-under-test.

Author: phil-davis

tests/acceptance/run.sh

@@ -1063,10 +1063,21 @@ then
 	done
 fi
 
+if [ -z "${APP_NAME}" ]
+then
+	APP_NAME=""
+fi
+
 #Enable and disable apps as required for default
 if [ -z "${APPS_TO_DISABLE}" ]
 then
-	APPS_TO_DISABLE="firstrunwizard notifications"
+  if [[ "${APP_NAME}" == "notifications" ]]; then
+    APPS_TO_DISABLE="firstrunwizard"
+  elif [[ "${APP_NAME}" == "firstrunwizard" ]]; then
+    APPS_TO_DISABLE="notifications"
+  else
+    APPS_TO_DISABLE="firstrunwizard notifications"
+  fi
 fi
 
 if [ -z "${APPS_TO_ENABLE}" ]