[cfg] Change ipv6 default to disabled

There is some issue with OwnTone's Airplay ipv6 implementation so disable ipv6
in the config until it is fixed.

Ref issue #1752

owntone.conf.in

@@ -45,7 +45,7 @@ general {
 #	trusted_networks = { "localhost", "192.168", "fd" }
 
 	# Enable/disable IPv6
-	ipv6 = yes
+#	ipv6 = no
 
 	# Set this if you want the server to bind to a specific IP address. Can
 	# be ipv6 or ipv4. Default (commented out or "::") is to listen on all

src/conffile.c

@@ -53,7 +53,7 @@ static cfg_opt_t sec_general[] =
     CFG_INT("websocket_port", 3688, CFGF_NONE),
     CFG_STR("websocket_interface", NULL, CFGF_NONE),
     CFG_STR_LIST("trusted_networks", "{localhost,192.168,fd}", CFGF_NONE),
-    CFG_BOOL("ipv6", cfg_true, CFGF_NONE),
+    CFG_BOOL("ipv6", cfg_false, CFGF_NONE),
     CFG_STR("bind_address", NULL, CFGF_NONE),
     CFG_STR("cache_path", STATEDIR "/cache/" PACKAGE "/cache.db", CFGF_NONE),
     CFG_INT("cache_daap_threshold", 1000, CFGF_NONE),