Config: skip empty options

When a config file contained an option with an empty value this would
override the value loaded from previous config files and set it to
nothing. This resulted in some very weird behaviour when resource caches
were not being synchronized.

This commit fixes the problem by skipping options with no values

Signed-off-by: Ondrej Lichtner <olichtne@redhat.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Config: print information about loading a conf file

We agreed that it would be a good idea to print information about loaded
config files. The original idea was to print this information to the
debug logs. However config files are loaded before logging is
initialized so that is not possible. Instead I used a simple print.

Signed-off-by: Ondrej Lichtner <olichtne@redhat.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
SlavePool: add information about pool machines

This commit changes how LNST presents information about loaded pool
machines.

* the query messages were moved to debug logs
* added info messages about which pool directory is being processed
* after a directory is loaded, a colorized summary of availability is
  printed

I also adjusted what happens to virt machines when virtualization is
disabled but the machiens are available. In that case the libvirt_domain
attribute is ignored meaning that the machine will only be used in the
matching algorithm for static interfaces.

If a machine will be used in the dynamic interfaces matching algorithm
it will have its libvirt_domain printed in the summary described above.

Signed-off-by: Ondrej Lichtner <olichtne@redhat.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>