LU-837 release semaphore for error case in gss_do_ctx_init_rpc

LU-837 release semaphore for error case in gss_do_ctx_init_rpc

in gss_do_ctx_init_rpc, the r/w lock "obd->u.cli.cl_sem" is not released
if the obd->u.cli.cl_import is NULL and returns error.

Change-Id: Ib9bb4d4cb79adabe8ff661b9b4a7f6df5963d4ff
Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1705
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>