Fix crash in ApnSettings.

ApnSettings runs with uid android.uid.phone and since it doesn't has
the MANAGE_DEVICE_ADMINS and MANAGE_PROFILE_AND_DEVICE_OWNERS
permission, show the generic support instead of the admin specific
message.

Bug: 27826969
Change-Id: I556a8b74aa1f692ebac1f4e30aeab3ed78ec5078