Update st2common.log.setup function so it takes new "st2_config_path" and supports logging config paths which are relative to st2.conf file directory.
Update st2common.log.setup function so it takes new "st2_config_path"
and supports logging config paths which are relative to st2.conf file
directory.

StackStorm/st2,StackStorm/st2,nzlosh/st2,Plexxi/st2,StackStorm/st2,Plexxi/st2,StackStorm/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2,nzlosh/st2,nzlosh/st2