global: create /var/run/ceph on daemon startup

This handles cases where the daemon is started without the benefit of
sysvinit or upstart (as with teuthology or ceph-fuse).

Signed-off-by: Sage Weil <sage@inktank.com>
init-ceph: look to ceph.conf instead of hard-coding /var/run/ceph

It could be elsewhere!

Signed-off-by: Sage Weil <sage@inktank.com>
vstart.sh: set var_run_dir to out

This avoids annoying errors about creating /var/run/ceph from init-ceph.

Fixes: #4036
Signed-off-by: Sage Weil <sage@inktank.com>