vty: Fix compiler warning about type changes

osmo_client_main.c:57:2: warning: initialization from incompatible pointer type
  .go_parent_cb = osmopcap_go_parent,
  ^
osmo_client_main.c:57:2: warning: (near initialization for ‘vty_info.go_parent_cb’)
  CCLD     osmo_pcap_client
  CC       osmo_server_main.o
osmo_server_main.c:56:2: warning: initialization from incompatible pointer type
  .go_parent_cb = osmopcap_go_parent,
  ^
osmo_server_main.c:56:2: warning: (near initialization for ‘vty_info.go_parent_cb’)

Change-Id: If73c85a64789ef4bff63dcfe008e918e650b428f
diff --git a/src/osmo_common.c b/src/osmo_common.c
index b97394e..33ec1b2 100644
--- a/src/osmo_common.c
+++ b/src/osmo_common.c
@@ -63,7 +63,7 @@
 	"There is NO WARRANTY, to the extent permitted by law.\r\n";
 
 
-enum node_type  osmopcap_go_parent(struct vty *vty)
+int osmopcap_go_parent(struct vty *vty)
 {
 	switch (vty->node) {
 	case CLIENT_NODE: