mount.ceph.c: free memory before return

CID 1219610 (#1 of 1): Resource leak (RESOURCE_LEAK)
 leaked_storage: Variable buf going out of scope leaks the
  storage it points to.
 leaked_storage: Variable mount_path going out of scope leaks
  the storage it points to.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>