Only change permission groups which should be changed

During a permission grant session multiple permission groups might get
granted. Permission groups might have foreground and backgroup
subgroups. Inside of the permission grant flow foreground and background
permissions are treated both as top-level groups. I.e. both have a
GroupState object.

We do not show UI for the groups which are already granted, we just mark
them as "SKIPPED".

If we have a permission group where the foreground permission was
granted but the background permission was not granted state at the
beginning is

foreground-group-state : SKIPPED
background-group-state : UNKNOWN

Then the UI might report e.g. "DENIED". In this case the deny should
only affect the background group as the UI was only shown for the
background group.

Test: 1. Granted fg permission
      2. Asked for both fg and bg permission
         -> This just marks the fg permission request as SKIPPED
      3. denied bg permission
      4. Only bg permisison was revoked (not fg permission)

Change-Id: Ifca7221f5ef331f0ad6fa51316ad62bfcb539a50