EX-3825 pcc: Check if PCC copy is unlinked for state output

EX-3825 pcc: Check if PCC copy is unlinked for state output

In this patch, it adds support for the command "lfs pcc state" to
check whether the PCC copy is in the local client cache or
unlinked improperly.

Test-Parameters: testlist=sanity-pcc env=ONLY=48
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: Ic50c901df78adfaf5b56990120f832e5d74a117c
Reviewed-on: https://review.whamcloud.com/45082
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>