search path for configuration file not covering all documented cases (relative to executable)

[ctheune]

The documentation shows two variants of supervisor(d|ctl) picking up the config file, two of which are "relative to the executable":

 5. ../etc/supervisord.conf (Relative to the executable)
 6. ../supervisord.conf (Relative to the executable)

However, the code for that search is highly dependent on the current working directory as it takes sys.argv[0] without paying attention to making the executable path absolute first. So if you, for example, enter the bin/ directory of a virtualenv and run ./supervisorctl, then the '../etc/supervisord' will never match because using dirname() on ./supervisorctl won't always give you the parent directory.

I suggest to using os.path.abspath (which will automatically pick up the cwd) and explicitly joining that with '../etc/supervisord.conf'), the same for variant 6.