Prevent Storage spoke Done button method from multiple launch

This happens when user clicking on Done button very fast.

Add flag which is reset when user enter the storage spoke.

pyanaconda/ui/gui/spokes/storage.py

@@ -250,6 +250,7 @@ def __init__(self, *args, **kwargs):
         self.encrypted = False
         self.passphrase = ""
         self.selected_disks = self.data.ignoredisk.onlyuse[:]
+        self.backclicked = False
 
         # This list contains all possible disks that can be included in the install.
         # All types of advanced disks should be set up for us ahead of time, so
@@ -461,6 +462,8 @@ def _on_disk_focus_in(self, overview, event):
     def refresh(self):
         self.disks = getDisks(self.storage.devicetree)
 
+        self.backclicked = False
+
         # synchronize our local data store with the global ksdata
         disk_names = [d.name for d in self.disks]
         # don't put disks with hidden formats in selected_disks
@@ -734,6 +737,13 @@ def on_back_clicked(self, button):
         # user might want to change settings presented in the dialogs shown from
         # within this method.
 
+        # Do not enter this method multiple times if user clicking multiple times
+        # on back button
+        if self.backclicked:
+            return
+        else:
+            self.backclicked = True
+
         # Remove all non-existing devices if autopart was active when we last
         # refreshed.
         if self._previous_autopart: