scsi: be2iscsi: Check tag in beiscsi_mccq_compl_wait

scsi: be2iscsi: Check tag in beiscsi_mccq_compl_wait

scsi host12: BS_1377 : mgmt_invalidate_connection Failed for cid=256
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff81332ebf>] __list_add+0xf/0xc0
PGD 0
Oops: 0000 [#1] SMP
Modules linked in:
...
CPU: 9 PID: 1542 Comm: iscsid Tainted: G               ------------ T 3.10.0-514.el7.x86_64 #1
Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 09/12/2016
task: ffff88076f310fb0 ti: ffff88076bba8000 task.ti: ffff88076bba8000
RIP: 0010:[<ffffffff81332ebf>]  [<ffffffff81332ebf>] __list_add+0xf/0xc0
RSP: 0018:ffff88076bbab8e8  EFLAGS: 00010046
RAX: 0000000000000246 RBX: ffff88076bbab990 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff880468badf58 RDI: ffff88076bbab990
RBP: ffff88076bbab900 R08: 0000000000000246 R09: 00000000000020de
R10: 0000000000000000 R11: ffff88076bbab5be R12: 0000000000000000
R13: ffff880468badf58 R14: 000000000001adb0 R15: ffff88076f310fb0
FS:  00007f377124a880(0000) GS:ffff88046fa40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 0000000771318000 CR4: 00000000001407e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
ffff88076bbab990 ffff880468badf50 0000000000000001 ffff88076bbab938
ffffffff810b128b 0000000000000246 00000000cf9b7040 ffff880468bac7a0
0000000000000000 ffff880468bac7a0 ffff88076bbab9d0 ffffffffa05a6ea3

Call Trace:
[<ffffffff810b128b>] prepare_to_wait+0x7b/0x90
[<ffffffffa05a6ea3>] beiscsi_mccq_compl_wait+0x153/0x330 [be2iscsi]
[<ffffffff810b1600>] ? wake_up_atomic_t+0x30/0x30
[<ffffffffa05981b1>] beiscsi_ep_disconnect+0x91/0x2d0 [be2iscsi]
[<ffffffffa0202ffa>] iscsi_if_ep_disconnect.isra.14+0x5a/0x70 [scsi_transport_iscsi]
[<ffffffffa02042fb>] iscsi_if_recv_msg+0x113b/0x14a0 [scsi_transport_iscsi]
[<ffffffff811dffd8>] ? __kmalloc_node_track_caller+0x58/0x290
[<ffffffffa02046ee>] iscsi_if_rx+0x8e/0x1f0 [scsi_transport_iscsi]
[<ffffffff815a351d>] netlink_unicast+0xed/0x1b0
[<ffffffff815a38fe>] netlink_sendmsg+0x31e/0x690
[<ffffffff815a03e4>] ? netlink_rcv_wake+0x44/0x60
[<ffffffff815a19e3>] ? netlink_recvmsg+0x1e3/0x450

beiscsi_mccq_compl_wait gets called even when MCC tag allocation failed
for mgmt_invalidate_connection.  mcc_wait is not initialized for tag 0
so causes crash in prepare_to_wait.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>