Return empty string if unable to read from some files during fact gathering so…

Return empty string if unable to read from some files during fact gathering so as not to change the values we return

lib/ansible/module_utils/facts.py

@@ -190,7 +190,7 @@ class Facts(object):
                 # if that fails, skip it
                 rc, out, err = module.run_command(fn)
             else:
-                out = get_file_content(fn)
+                out = get_file_content(fn, default='')
 
             # load raw json
             fact = 'loading %s' % fact_base
@@ -1680,7 +1680,7 @@ class LinuxNetwork(Network):
             device = os.path.basename(path)
             interfaces[device] = { 'device': device }
             if os.path.exists(os.path.join(path, 'address')):
-                macaddress = get_file_content(os.path.join(path, 'address'))
+                macaddress = get_file_content(os.path.join(path, 'address'), default='')
                 if macaddress and macaddress != '00:00:00:00:00:00':
                     interfaces[device]['macaddress'] = macaddress
             if os.path.exists(os.path.join(path, 'mtu')):
@@ -1703,15 +1703,15 @@ class LinuxNetwork(Network):
                 interfaces[device]['type'] = 'bridge'
                 interfaces[device]['interfaces'] = [ os.path.basename(b) for b in glob.glob(os.path.join(path, 'brif', '*')) ]
                 if os.path.exists(os.path.join(path, 'bridge', 'bridge_id')):
-                    interfaces[device]['id'] = get_file_content(os.path.join(path, 'bridge', 'bridge_id'))
+                    interfaces[device]['id'] = get_file_content(os.path.join(path, 'bridge', 'bridge_id'), default='')
                 if os.path.exists(os.path.join(path, 'bridge', 'stp_state')):
                     interfaces[device]['stp'] = get_file_content(os.path.join(path, 'bridge', 'stp_state')) == '1'
             if os.path.exists(os.path.join(path, 'bonding')):
                 interfaces[device]['type'] = 'bonding'
-                interfaces[device]['slaves'] = get_file_content(os.path.join(path, 'bonding', 'slaves')).split()
-                interfaces[device]['mode'] = get_file_content(os.path.join(path, 'bonding', 'mode')).split()[0]
-                interfaces[device]['miimon'] = get_file_content(os.path.join(path, 'bonding', 'miimon')).split()[0]
-                interfaces[device]['lacp_rate'] = get_file_content(os.path.join(path, 'bonding', 'lacp_rate')).split()[0]
+                interfaces[device]['slaves'] = get_file_content(os.path.join(path, 'bonding', 'slaves'), default='').split()
+                interfaces[device]['mode'] = get_file_content(os.path.join(path, 'bonding', 'mode'), default='').split()[0]
+                interfaces[device]['miimon'] = get_file_content(os.path.join(path, 'bonding', 'miimon'), default='').split()[0]
+                interfaces[device]['lacp_rate'] = get_file_content(os.path.join(path, 'bonding', 'lacp_rate'), default='').split()[0]
                 primary = get_file_content(os.path.join(path, 'bonding', 'primary'))
                 if primary:
                     interfaces[device]['primary'] = primary