slapos_web: form post can send "shared" in many formats.

master/bt5/slapos_web/SkinTemplateItem/portal_skins/vifib_hosting/SoftwareRelease_requestFromDialog.py

@@ -3,9 +3,10 @@ portal = context.getPortalObject()
 if shared == "true":
   shared = True
   
-if shared == "false":
+if shared in ["false", "", None]:
   shared = False
 
+
 if not service_title:
   raise ValueError("Service Title is mandatory!")