packets: fix use of potentially uninitialized value
Merge pull request #7 from mehlis/master

packets: fix potentially return of uninitialized variable

When the flags field of a pdu was not 0 or 1 the value of an uninitialized variable was returned.
In the current code path this could not happen because  rtr_update_pfx_table() was always called before rtr_undo_update_pfx_table(). rtr_update_pfx_table() ensures that the flag value is 0 or 1.