BlackBerry: Increased loop level around bps_get_event

This is needed, because bps_get_event can also invoke callbacks.
Deferred deletions in such a callback are not executed for instance,
because the loop level might already be at its minimum.

Change-Id: I8a1b3a3f92de139575654de011352f8abc6c3c1a
Reviewed-by: Kevin Krammer <kevin.krammer@kdab.com>
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Jeff Kehres <jkehres@rim.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>