[BUG/CLEANUP] cookiedomain -> cookie_domain rename + free(p->cookie_domain)

Rename cookiedomain -> cookie_domain to be consistent with current
naming scheme. Also make sure cookie_domain is deallocated at deinit()
diff --git a/src/haproxy.c b/src/haproxy.c
index fc82d2f..b42728e 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -658,6 +658,9 @@
 		if (p->cookie_name)
 			free(p->cookie_name);
 
+		if (p->cookie_domain)
+			free(p->cookie_domain);
+
 		if (p->url_param_name)
 			free(p->url_param_name);