Merge pull request #5622 from ceph/wip-memstore

MemStore locking enhancements and bufferlist alternative

Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Haomai Wang <haomaiwang@gmail.com>

diff --cc ceph.spec.in
Simple merge

diff --cc src/common/config_opts.h
Simple merge

diff --cc src/os/Makefile.am
Simple merge

diff --cc src/test/Makefile-client.am
Simple merge