parking_tests: Fix assertions and possibly crashes in res_parking unit tests

Assertions were caused by attempting to play music on hold to a channel with
no formats. Parking unit test channels were given formats and a technology so
that they would be able to pretend to read/write frames.

ASTERISK-24413 #close
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/4075/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@425611 f38db490-d61c-443f-a65b-d21fe96a405b