Code cleanup

[jouvin]

After the important code cleanup done as part of 14.6 (#6), a few more cleanups are still needed in ncm-cdispd. This includes:

• Use getTree() API to make the code simpler and easier to maintain
• Remove global declaration of variables at the head of each functions: most of these variables can in fact have a smaller scope
• Use real constants for variables used as constants (e.g. $path)
• Fix the "splitted" else constructs that resulted from code reformatting done in 14.6. Look for lines like:

}
else {

[jouvin]

At this point, all the changes planned have been done... the result is a major rewrite of ncm-cdispd. It has been deployed on a test system and seems to work but clearly, as pointed in #7, the lack of unit test makes difficult to be very confident in such a rewrite... To address this, I plan to break ncm-cdispd in 2 parts:

• ncm-cdispd script itself that will be mainly the main loop and the init_components() function. This part will remain hard to test except by deploying it.
• Every else (in package main) moved to a new package to be installed in /usr/lib/perl, CDISPD::Utils. This part will be eligible to unit testing and as this is the real workhorse of ncm-cdispd, this should guarantee that further modifications don't break it.

[jouvin]

As part of the code cleanup, I'd like to improve the way ncm-cdispd handles/processes signals to avoid aborting YUM transactions during upgrades. See https://github.com/quattor/configuration-modules-core/issues/242#issuecomment-49515800. Hopefully everything should be ready for 14.8.

[jrha]

I'm going to consider this closed by #11, anything remaining can have new issues opened.