Fix jenkins restart on Linux after a JRE system update

Daemon.getCurrentExecutable() use /proc/PID/exe to retrieve the used JRE. This link is broken when the target changes (ie after a JRE system update) because the kernel appends ' (deleted)' to the symlink. This patch uses the first argument of the command line (in /proc/PID/cmdline) instead.
Merge pull request #1192 from ydubreuil/fix-restart-after-jre-system-update

Fix jenkins restart on Linux after a JRE system update