support "if exists then <action>" for testing that the process doesn't exist

[Tildeslash]

It could be useful to support test for making sure some process doesn't run.

For example:

check process myproc matching "abcd"
    if exist then exec "/etc/init.d/myproc stop"

Could be useful also for other checks (file, directory, etc. to trigger some action if file/directory/etc. was created).

[Jess Bermudes]

This feature would also be useful to check if files exist for diagnostic reasons, like how in Ubuntu if the system needs a reboot to apply software updates the file /var/run/reboot-required will exist. So this is a good idea.

[Tildeslash]

implemented in Monit 5.21.0