icinga: fix jenkins monitoring

622bf3a8 / https://gerrit.wikimedia.org/r/#/c/58489/ tweaked the jenkins
command like to define a java system property. That makes check_jenkins
unable to find the process.  Using a wildcard regex between java and the
-jar would let us catch the jenkins process no matter how many system
properties we can set.

Change-Id: I58532453961c8c8ddc9d2c7fd723dbdad172a615