LU-2790 ldlm: handle lvbo_init failure in ldlm_resource_get

Under some special cases, such as RAM pressure, lvbo_init()
may be failed, then the caller - ldlm_resource_get() should
handle the failure to prevent subsequent operations to use
non-exist resource.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I0eabbf5daaaba9aa163a45f24b6b621477ec4d32
Reviewed-on: http://review.whamcloud.com/5699
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>