s3/modules: New vfs module: cephfs

Implements a vfs module for cephfs, a distributed file system
with posix semantics, built on the ceph distributed object
storage layer.  The ceph vfs module interfaces to the libcephfs
userspace API, and is primarily a lightweight wrapper around
libcephfs, translating error codes and parameters as necessary.

Signed-off-by: Sam Lang <sam.lang@inktank.com>
source4/libcli: Only set ctemp set on success

If open fails ctemp.out.name probably won't be valid and strdup
will cause a segv.  Only set the path if open succeeds.

Signed-off-by: Sam Lang <sam.lang@inktank.com>