cleanup: removed last references to globals from client

- There were some refs in SyntheticClient to g_(ceph_context|conf), I
  replaced them with client->cct and client->cct->_conf.
- There were some refs in fuse_ll to g_conf, also replaced them with
  client->cct or cfuse->client->cct where applicable.

This makes everything in src/client completely independent from globals.

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>
cleanup: removing refs to globals from libosd

Removed almost all references to globals, apart from two;

- In OSD.cc: reference to g_lockdep
- In PG.h: NamedState uses ceph_clock_now(g_ceph_context)

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>
cleanup: removing globals from common/obj_bencher

This file is in common/ but cant be included in libcommon.la because of
this reference. Removing it, making the binary calling it to pass the
correct cephcontext (rados, rest-bench).

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>
cleanup: reduced number of pointer indirection in osd

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>