Remove symlink to vrouter.ko only during uninstallation

RPM Scriplets execution order during upgrade, installs the new package first
followed by new packages's postinst and then preun script of old package
Because of this, symlink gets removed during contrail upgrade

Closes-Bug: 1623413
Change-Id: I122129608e8fd4749968b610987131162c62e46e

rpm/contrail/contrail.spec

@@ -160,8 +160,14 @@ The OpenContrail vRouter is conceptually similar to existing commercial and open
 The package opencontrail-vrouter-dkms provides the OpenContrail Linux kernel module.
 
 %preun vrouter
-if [ -L /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko ]; then
-    rm -f /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko
+# Execute only during uninstall, skip during upgrade
+if [ $1 == 0 ]; then
+    if [ -L /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko ]; then
+        echo "Removing symbolic link /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko"
+        rm -f /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko
+    fi
+else
+    echo "Skip removing /lib/modules/$(uname -r)/extra/net/vrouter/vrouter.ko for upgrade"
 fi
 exit 0