Recording: bbb-record --rebuild restarts processing at the sanity step

Previously, bbb-record --rebuild was restarting recording processing
from scratch by creating the .../recording/<meeting_id>.done file. This
causes the recording to be reprocessed starting at the archive step.
However, re-running the archive step for an existing meeting is not
really supported! Ever since the segmented recording code was added, it
shouldn't /corrupt/ the recording files, but it's still not good.

And as a side-effect, re-running the archive step will re-create the
.norecord file for meetings without recording marks, meaning that you
cannot use bbb-record --rebuild to force a recording without marks to be
processed.

Switch bbb-record to restart recording processing at the sanity stage to
match the BBB 2.2 behaviour. Rather than have it insert tasks directly
into resque via redis-cli, it goes through a ruby wrapper that performs
input validation and uses the resque apis.