LU-10656 ldlm: fix export reference

LU-10656 ldlm: fix export reference

In ptlrpc_connect_interpert, the export reference could be
leaked if there is error before the following class_exp_put.

Lustre-change: https://review.whamcloud.com/31139
Lustre-commit: e52f2ea40e55d13b2f14fccd04959584c9022dbd

Change-Id: I9ddd82fa1bbf8e17079e9746202be63e6233c052
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/31636
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>