slapos_jio: sanitize slapos master monitoring url

3 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
canceled SlapOS-Master.UnitTest-Master

01:00:18

failed SlapOS.Eggs.UnitTest-Master.Python2

00:13:50

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:25