Allow release version builds for make release-test-*

This fixes #41

scripts/kubeadm_test.sh

@@ -13,7 +13,7 @@ install_version="contiv-${BUILD_VERSION:-devbuild}"
 default_net_cidr="${DEFAULT_NET:-20.1.1.0/24}"
 
 # For local builds, copy the build binaries to the vagrant node, using the vagrant ssh-key
-if [ "$install_version" = "contiv-devbuild" ];then
+if [ -f "release/${install_version}.tgz" ];then
   pushd cluster
   ssh_key=$(CONTIV_KUBEADM=1 vagrant ssh-config contiv-node1 | grep IdentityFile | awk '{print $2}' | xargs)
   popd

scripts/swarm_test.sh

@@ -16,7 +16,7 @@ popd
 # Extract and launch the installer
 mkdir -p release
 cd release
-if [ "$install_version" != "contiv-devbuild" ];then
+if [ ! -f "${install_version}.tgz" ];then
   # For release builds, get the build from github releases
   curl -L -O https://github.com/contiv/install/releases/download/${BUILD_VERSION}/${install_version}.tgz
 fi