test/twisted/test-plugin.c: don't leak McdDispatcherContext in reject_with_reason, reject_rickrolling
test/twisted/test-plugin.c: don't leak McdDispatcherContext in reject_with_reason, reject_rickrolling

Oops... this is a memory leak, and could also prevent Finished from being
emitted from the corresponding dispatch operations.

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control