- sleep_on() is known to be racy replacing it with OBD_SLEEP_ON()
  - added OBD_SLEEP_ON() which is inspired by wait_event() macro.
  - inter_module_{get|put}() replaced with symbol_{get|put}()

- fixes in GNS stuff:
  - ll_revalidate_it() calls missed ll_intent_release() in the case
    GNS dentry is found (fix for #6176)

  - added ll_gns_send_signal() which is needed to cause syscall restarting in the
    case of -ERESTARTSYS is returned.

  - cleanups in ll_gns_mount_object()

  - ll_gns_mount_object() does not wait unconditionaly for userspace upcall,
    instead it give it some time to complete (10s) and returns error if it
    did not mount dentry. This fixes the case when upcall script runs endless
    loop and never returns. This also fixes possible deadlock if another thread
    with wait on not finished mount (this schema is disabled by and -ERESTARTSYS
    is used instead. Both, waiting aproach and -ERESTARTSYS one need more
    investigation).

  - handling result of inode_setattr() call. Printing error message on error.
    This fixes wanings that result of calling this function should be checked.

  - fixed debug message about GNS inabilty to mount dentry (missed arg to CDEBUG
    format string)

  - cleanups in obdfilter_init()
  - fixed using "mount" command in sanity-gns.sh