pf tests: basic SCTP connection test

pf can now inspect SCTP. Check that we can set up a connection.
IPv4 and IPv6 tests.

MFC after: 3 weeks
Sponsored by: Orange Business Services
Differential Revision: https://reviews.freebsd.org/D40863

(cherry picked from commit 95363473793986eeecf19f7ed78d05f25cfa7b87)