jenkins: check for IU properly

The bug fixed by Idb034bf2ae749204836ab7e02018d769bb242a9f was not
detected by jenkins because it installs libosmo-sccp unconditionally.

Let's be more strict and install it only when necessary for IU builds to
make sure we can catch such bugs in future.

Change-Id: I573c7fec687edb71d79815b38a3bcf96273c03b3
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index dc1a1a5..140fc63 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -26,10 +26,10 @@
 
 osmo-build-dep.sh libosmo-abis
 osmo-build-dep.sh libosmo-netif
-osmo-build-dep.sh libosmo-sccp
 osmo-build-dep.sh osmo-ggsn
 
 if [ "x$IU" = "x--enable-iu" ]; then
+    	osmo-build-dep.sh libosmo-sccp
 	osmo-build-dep.sh libasn1c
 	#osmo-build-dep.sh asn1c aper-prefix # only needed for make regen in osmo-iuh
 	osmo-build-dep.sh osmo-iuh