Gallery2: fix permission issue

Gallery app is signed with platform key for APN settings. However,
being a platform_app causes certain SELinux permission denials.
As APN settings are actually delegated to Settings app, APN name query
code can be removed from Gallery app, so that platform signature is no
longer required.

Change-Id: I269bb424facf09af1ff9549d77dd6e2022988ed0
CRs-Fixed: 960252
CRs-Fixed: 946086