stasis: Add methods to allow for synchronous publishing to subscriber

This patch adds an API call to Stasis that allows a publisher to publish a
stasis message that will not return until a specific subscriber handles the
message. Since a subscriber can have their own forwarding topic which orders
messages from many topics, this allows a publisher who knows of that subscriber
to synchronize to that subscriber regardless of the forwarding relationships
between topics.

This is of particular use for dialplan applications that need to synchronize
on a particular subscriber's handling of a message.

(issue ASTERISK-22884)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3099/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@405311 f38db490-d61c-443f-a65b-d21fe96a405b
CDRs: Synchronize dialplan applications that manipulate CDRs with the engine

In https://reviewboard.asterisk.org/r/3057/, applications and functions that
manipulate CDRs were made to interact over Stasis. This was done to
synchronize manipulations of CDRs from the dialplan with the updates the
engine itself receives over the message bus.

This change rested on a faulty premise: that messages published to the CDR
topic or to a topic that forwards to the CDR topic are synchronized with the
messages handled by the CDR topic subscription in the CDR engine. This is not
the case. There is no ordering guaranteed for two messages published to the
same topic; ordering is only guaranteed if a message is published to the same
subscriber.

Stasis was modified in r405311 to allow a publisher to synchronize on the
subscriber. This patch uses that API to synchronize the CDR publishers with
the CDR engine message router, which maintains the overall topic subscription.

(closes issue ASTERISK-22884)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3099/



git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@405312 f38db490-d61c-443f-a65b-d21fe96a405b