pf: move pf_test_rule() out of pf_setup_pdesc()

Move the call to pf_test_rule() for fragments that have not been
reassembled by normalization from pf_setup_pdesc() to pf_test().
This simplifies the paramter list of pf_setup_pdesc() as it can
concentrate on its job filling the pf_pdesc struct.
ok henning mpf

Obtained from: OpenBSD, bluhm <bluhm@openbsd.org>, fb9fe53b92
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D46935