librados: add timeout to wait_for_osdmap()

librados: add timeout to wait_for_osdmap()

This is used by several pool operations independent of the objecter,
including rados_ioctx_create() to look up the pool id in the first
osdmap.

Unfortunately we can't just rely on WaitInterval returning ETIMEDOUT,
since it may also get interrupted by a signal, so we can't avoid
keeping track of time explicitly here.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
(cherry picked from commit 1829d2c9fd13f2cbae4e192c9feb553047dad42c)

Conflicts:
	src/librados/RadosClient.cc