Jenkinsfile: Handle special case for release image type

The "release" image is the default image without any suffix. ie:
netmodule-linux-image. It needs a special handling because the name of
the image type ('release') does not match with the image suffix
(nothing).

Jenkinsfile

@@ -97,6 +97,10 @@ def build_and_deploy() {
         build(params.IMAGE_TYPE, params.IMAGE_TYPE, true)
         deploy(params.IMAGE_TYPE, true)
     }
+    else if (params.IMAGE_TYPE == 'release') {
+        build('ostree', '', false)
+        deploy('', false)
+    }
     else {
         build('ostree', params.IMAGE_TYPE, false)
         deploy(params.IMAGE_TYPE, false)