Merge pull request #6686 from stiopaa1/namespace_buffer

common: use namespace instead of subclasses for buffer

Reviewed-by: Sage Weil <sage@redhat.com>

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

diff --cc src/journal/Journaler.h
Simple merge

diff --cc src/librbd/ImageCtx.h
Simple merge

diff --cc src/librbd/internal.h
Simple merge

diff --cc src/osd/PG.h
Simple merge