LU-11407 tgt: cleanup job_stats output printing

LU-11407 tgt: cleanup job_stats output printing

Escape non-printable and other special characters in the JobID
name, which may be passed from the client environment, to avoid
breaking YAML format parsing.  We can't use the kernel "%*pE"
escape format, because that doesn't have any option to escape
printable characters like quotes or regular spaces.

Lustre-change: https://review.whamcloud.com/37764
Lustre-commit: 338381574b643da064e90e44d75be85d1be3a93c

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: If6a0bc4276fae03305f94e8c85d8f109913ebbe5
Reviewed-by: Ben Evans <beevans@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-on: https://review.whamcloud.com/48539
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>