cleanup: globals from libosd

There are some new globals introduced in libosd lately. This patch
cleans them.

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>
cleanup: passing context to NamedState for ceph_clock

This makes the constructor call on the subclasses explicit, and passes
the cct to the NamedState constructor. This cct is used by ceph_clock
to set enter_time.

Removes the last reference to g_ceph_context from libosd.

Signed-off-by: Roald J. van Loon <roaldvanloon@gmail.com>
Merge pull request #568 from roaldvanloon/wip-cleanup-globals

Wip cleanup globals

Reviewed-by: Sage Weil <sage@inktank.com>