postmaster -S will not print an error if pid file exists

If a second postmaster is started on a data directory and the second one
uses the -S option it will not print a message but simply exit and not
start a background process.  The exit status is 0.

This seems to have gotten lost in the changes postmaster.c rev. 1.195,
global lock file changes by tgl.

-- 
Peter Eisentraut      peter_e@gmx.net       http://yi.org/peter-e/