NVDA-86 pcc: print kern_path() error on failure

NVDA-86 pcc: print kern_path() error on failure

When looking up a PCC cache pathname in kern_path() returns an error,
print the pathname and returned error before it is ignored.

Test-Parameters: trivial testlist=sanity-pcc
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I9ef59ffedc2c6d11cc7ab1abb4098c56f23ebbe5
Reviewed-on: https://review.whamcloud.com/44962
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yingjin Qian <qian@ddn.com>