[Bug 235723] Starting GF on port which is already used results into neverending GF start

There is quite long timeout when GF server is starting and if there is 
an issue with occupied HTTP listener port, this Start Task will consume 
all timeout (around 5 minutes) and block server usage.

Trunk fix adds 'kill' task to allow user to handle this problem 
immediately and also HTTP listener port availability check was added to 
prevent starting server when those conditions exists.

For 7.4 _only_ port availability check will be backported, because 
'kill' task contains too many code changes.

changeset: 263606:8a673279b136
summary: #235723 - Added simple HTTP port availability check before 
start. Fix to be backported into 7.4