Change JACK_DEFAULT_SELF_CONNECT_MODE to "allow"

The constant was introduced when the mode parameter of the JackEngine
constructor was added in aab13501f4.
Then in 6253344da6 the parameter
was exposed through the control api, but with different default
value.

This commit changes the value to match the default of the control api
parameter.

common/JackConstants.h

@@ -84,6 +84,6 @@
 #define EMPTY   0xFFFD
 #define FREE	0xFFFC
 
-#define JACK_DEFAULT_SELF_CONNECT_MODE JackSelfConnectIgnoreAll
+#define JACK_DEFAULT_SELF_CONNECT_MODE JackSelfConnectAllow
 
 #endif