Revert "kvm: Bang immediately in case of vnc_promise problem"

This reverts commit d7721eb4.

The change didn't fix the real problem.

software/kvm/buildout.hash.cfg

@@ -19,7 +19,7 @@ md5sum = f2b0f1ed27148504f220e06eaceff935
 
 [template-kvm]
 filename = instance-kvm.cfg.jinja2
-md5sum = 0befc393a694885ce503589ccbdd59d7
+md5sum = 17c58f74d1ed4cb7dce11bf9af71dd33
 
 [template-kvm-cluster]
 filename = instance-kvm-cluster.cfg.jinja2.in

software/kvm/instance-kvm.cfg.jinja2

@@ -590,8 +590,6 @@ promise = check_socket_listening
 name = vnc_promise.py
 config-host = ${kvm-parameter-dict:vnc-ip}
 config-port = ${kvm-parameter-dict:vnc-port}
-result-count = 1
-failure-amount = 1
 
 [kvm-disk-image-corruption-bin]
 recipe = collective.recipe.template