TT#97150 increase length of src/dst-leg

Avoids truncated strings from Kamailio. This length is in line with what
we have in mr8.5+.

Change-Id: I3ea02012c674fb595dfa1071c81039ca7e8df25a
(cherry picked from commit ed398f3543)

mediator.h

@@ -75,8 +75,8 @@ typedef enum {
 
 
 typedef struct {
-    char src_leg[256];
-    char dst_leg[256];
+    char src_leg[1024];
+    char dst_leg[1024];
     char sip_code[4];
     char sip_reason[32];
     char callid[256];