EX-3478 pcc: avoid uninitialized pcc mutext lock in cleanup

EX-3478 pcc: avoid uninitialized pcc mutext lock in cleanup

Running racer concurrently crashed in the following way:
  RIP: 0010:[...]  [...] __list_add+0x1b/0xc0
  __mutex_lock_slowpath+0xa6/0x1d0
  mutex_lock+0x1f/0x2f
  pcc_inode_free+0x1e/0x60 [lustre]
  ll_clear_inode+0x64/0x6a0 [lustre]
  ll_delete_inode+0x5d/0x220 [lustre]
  evict+0xb4/0x180
  iput+0xfc/0x190
  ll_iget+0x156/0x350 [lustre]
  ll_prep_inode+0x212/0x9b0 [lustre]

After analysis, we found that the mutex @lli_pcc_lock is not
initialized. The reason is that ll_lli_init() is not called to
initialize @lli.
When call pcc_inode_free(), it will call mutex_lock() on the
uniniitialized @lli_pcc_lock, thus crash the kernel.

Test-Parameters: testlist=racer env=DURATION=3600
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: I612c79a5b8eb4fa9daeb9e446a457e95c666c04a
Reviewed-on: https://review.whamcloud.com/44300
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>