TT#68300 Set default values for most options

We should set sane defaults for almost all values. This will make it
possible to execute even when the configuration file is not present.

Change-Id: If85a72ad2b1470bdc9791e59810b4ba483becb9c

lib/NGCP/API/Client.pm

@@ -20,9 +20,9 @@ sub _load_config_defaults {
         or croak("Cannot read $cfg_file: $ERRNO");
 
     Readonly my $config => {
-        host          => $cfg->{_}->{NGCP_API_IP},
-        port          => $cfg->{_}->{NGCP_API_PORT},
-        iface         => $cfg->{_}->{NGCP_API_IFACE},
+        host          => $cfg->{_}->{NGCP_API_IP} // '127.0.0.1',
+        port          => $cfg->{_}->{NGCP_API_PORT} // 80,
+        iface         => $cfg->{_}->{NGCP_API_IFACE} // 'lo',
         sslverify     => $cfg->{_}->{NGCP_API_SSLVERIFY} // 'yes',
         sslverify_lb  => $cfg->{_}->{NGCP_API_SSLVERIFY_LOOPBACK} // 'no',
         read_timeout  => $cfg->{_}->{NGCP_API_READ_TIMEOUT} // 180,