library: Separate debug and info logs from warnings

Logs are now separed by severity level. Warnings and failures are the only logs
that appear now on the output. All logs are saved into a new json parameter
called "stderr" that is later shown on a different task. In case of
failure, all logs are shown as output. Tests have been created and modified in
order to assure that this feature works.

Signed-off-by: Elvira Garcia Ruiz <elviragr@riseup.net>

tasks/main.yml

@@ -64,6 +64,10 @@
     ignore_errors: "{{ network_ignore_errors | default(omit) }}"
     force_state_change: "{{ network_force_state_change | default(omit) }}"
     connections: "{{ network_connections | default([]) }}"
+  register: __network_connections_result
+
+- name: Show debug messages
+  debug: var=__network_connections_result
 
 - name: Re-test connectivity
   ping: