Wip cleanup globals

Removing references to globals in src/client (f7d96cb), src/osd (500bbe2) and src/common/obj_bencher (1a1382d) respectively.

Especially the second (osd) needs extensive review. I don't know if this has consequences I do not know about.

It will eventually be easier to build ceph, as only binaries need to be linked against libglobal when references to globals have been removed everywhere. Apart from that, I think that it is nicer if the binary sets the context - not the library itself.

This of course leaves mainly src/mon, src/mds and src/rgw. If the three in this pull request have been reviewed and tested (and I received the comments), I'll do these also.