Merge pull request #1002 from Chakerbh/gcp_destroy

Make sure that the machine is UP before trying to destroy it in GCP

Author: AmineChikhaoui

Diff for: nixops/backends/gce.py

@@ -652,6 +652,10 @@ def destroy(self, wipe=False):
         if not self.project:
             return True
 
+        if self.state != self.UP:
+            # The machine is down, we have nothing to do.
+            return True
+
         try:
             node = self.node()
             question = "are you sure you want to destroy {0}?"