Revert "monitor: enable IO thread for (qmp & !mux) typed"

Revert "monitor: enable IO thread for (qmp & !mux) typed"

This reverts commit 3fd2457d18edf5736f713dfe1ada9c87a9badab1.

Enabling OOB caused several iotests failures; due to the imminent
2.12 release, the safest action is to disable OOB for now.  If
other patches fix the issues that iotests exposed, it may be turned
back on in time for the release, otherwise it will be 2.13 material;
either way, the framework changes not reverted now do not hurt if
they remain as part of the 2.12 release.

Additionally, revert the tests in the patch 02130314d8 ("qmp: introduce
QMPCapability", 2018-03-19), as both parts must be reverted at once
to keep 'make check' passing.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180323140821.28957-2-peterx@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
[eblake: reorder/squash commits, enhance commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>