User permissions not synched when DEFAULT_ANONYMOUS_VIEW_PERMISSION is True

[giohappy]

When DEFAULT_ANONYMOUS_VIEW_PERMISSION is set to True Geofence rules are not synched when a new layer is uploaded. This prevents the user to see its own new layers.

This happens because the synch is never performed inisde the block afer this line.

A small refactoring is required and a call to
sync_geofence_with_guardian(layer, perms, user=None, group=None) should be enough to fix it.

[afabiani]

ref. GeoNode#5493

PR submitted GeoNode#5494