Lots of exchanges create problems during failover under high
load. Please see bug report for details.
This is step 1 in the process: only using default exchange
when publishing. Consumers will still consume on separate
exchanges (and on default exchange by default) so this
should be (and tested to be) a non-breaking and
upgrade-friendly change.
Step 2 is to update consumers to only listen on default exchange,
to happen in T release.
Change-Id: Id3603f4b7e1274b616d76e1c0c009d2ab7f6efb6
Closes-Bug: #1789177
(cherry picked from commit 3a5de89dd6)