<haproxy_ctld> Bug 920990 - fix p_usage showing usage message twice

updated p_usage method to drop straight out of program (via exit!) after
displaying usage instead of raising the "exit" exception
Bug 950823

Bash cannot stomach a function with empty body; this caused syntax
error, and the failure to create Ruby applications.
Merge pull request #2002 from dobbymoodge/BZ920990

<haproxy_ctld> Bug 920990 - fix p_usage showing usage message twice
Merge pull request #2013 from BanzaiMan/dev/hasari/bz950823

Bug 950823