Fix Settings app crash after enabled multi-user

Bug: 8128225
Change-Id: I2918a5ec36e861a1ce4b2e67cf7607929732a7bf
Fix NullPointerException at RunningState

getServiceInfo returns null if you have a service defined in the
manifest as: <service android:name=".Xxx" android:exported="false" />
or and in an <application> with no label or icon.
Dont crash the Settings application because of that.

Change-Id: I6f9f69c130e610b7e4ab66426177b7bade1e1515
Check if the Activity is finishing before showDialog()

Check if the Activity is going through its finishing phase before
displaying the Dialog, because Showing dialog once the activity
is no longer in context will cause BadTokenException.

Change-Id: I58940e694f61cd79536abe2df60a0b745a7b806f