msgr: maintain list of accepting pipes

New pipes exist in a sort of limbo before we know who the peer is and
add them to rank_pipe.  Keep a list of them in accepting_pipes for that
period.

Signed-off-by: Sage Weil <sage@inktank.com>
msgr: close accepting_pipes from mark_down_all()

We need to catch these pipes too, particularly when doing a rebind(),
to avoid them leaking through.

Signed-off-by: Sage Weil <sage@inktank.com>
msg/Pipe: hold pipe_lock during important parts of accept()

Previously we did not bother with locking for accept() because we were
not visible to any other threads.  However, we need to close accepting
Pipes from mark_down_all(), which means we need to handle interference.

Fix up the locking so that we hold pipe_lock when looking at Pipe state
and verify that we are still in the ACCEPTING state any time we retake
the lock.

Signed-off-by: Sage Weil <sage@inktank.com>
msg/Pipe: a bit of additional debug output

Signed-off-by: Sage Weil <sage@inktank.com>
osd: make 'from dead osd' message more informative

I thought I saw some weirdness here.

Signed-off-by: Sage Weil <sage@inktank.com>
asdf
temp debug