Make export vcf file names consistent

- Name the file in the same way as CP2
- Also add grant access to URI. There's no bug w/o it, but it's good practice
  based on document here: http://developer.android.com/training/secure-file-sharing/share-file.html#GrantPermissions

Bug 27298727

Change-Id: I77ac08c6a0be30b7ebf90cd519c2b14f8aa8dd37