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.

Lustre-change: https://review.whamcloud.com/37764
Lustre-commit: TBD (from 953c674fa9b9ae6f20e2cbdd8ed17cadd17922c9)

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: If6a0bc4276fae03305f94e8c85d8f109913ebbe5
Reviewed-on: https://review.whamcloud.com/45112
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>