pmrep: properly omit unit info with separate header when requested
pmrep: properly omit unit info with separate header when requested

Before:
$ pmrep -C -g -U mem.util.free
[ 1] - mem.util.free - Kbyte

         1

After:
$ pmrep -C -g -U mem.util.free
[ 1] - mem.util.free

         1

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp