Use more idiomatic python in VM filtering

qubesmanager/main.py

@@ -682,13 +682,10 @@ class VmManagerWindow(Ui_VmManagerWindow, QMainWindow):
 
     def showhide_vms(self, show_inactive, show_internal):
         if show_inactive and show_internal:
-            row_no = 0
-            while row_no < self.table.rowCount():
+            for row_no in xrange(self.table.rowCount()):
                 self.table.setRowHidden(row_no, False)
-                row_no += 1
         else:
-            row_no = 0
-            while row_no < self.table.rowCount():
+            for row_no in xrange(self.table.rowCount()):
                 widget = self.table.cellWidget(row_no,
                                                self.columns_indices["State"])
                 running = widget.vm.last_running
@@ -698,7 +695,6 @@ class VmManagerWindow(Ui_VmManagerWindow, QMainWindow):
                     self.table.setRowHidden(row_no, True)
                 else:
                     self.table.setRowHidden(row_no, False)
-                row_no += 1
 
     def mark_table_for_update(self):
         self.reload_table = True