gitclone: if directory is no longer present, install, never update.

slapos/recipe/gitclone.py

@@ -145,6 +145,10 @@ class Recipe(object):
       raise UserError('revision and branch (other than master) parameters '
           'are set but are incompatible. Please specify only one of them.')
 
+    # Check existence of directory
+    if not os.path.exists(self.location):
+      self.update = self.install
+
   def gitReset(self, revision=None):
     """Operates git reset on the repository."""
     command = [self.git_command, 'reset', '--hard']