fix whitespace in mysql nrpe check command

"nrpe::monitor_service { 'mysql disk space':"

from I100a7adb4211b7fc6f0e7a37471010d4371a795b

results in files with actual whitespace, like

file "check_mysql disk space.cfg"
check_mysql disk space.cfg: ASCII text

on the monitored servers

and errors like:

<+icinga-wm> PROBLEM - MySQL disk space on db35 is CRITICAL:
NRPE: Command check_mysql not defined

etc on all mysql servers

Change-Id: If0117511497ee1457e63d2710f1c3e29f4f44bc0