Fix work with --mbr=off.

pym/cl_install.py

@@ -2404,6 +2404,8 @@ class cl_install(color_print, SignalInterrupt):
     def checkCorrectBootRecordDisk(self):
         """Check boot record disk"""
         mbr = self.clVars.Get('os_install_mbr')
+        if mbr == "off" or mbr == "":
+            return True
         tableOnBootDisk = self.varSelect('os_device_table',
                 where="os_device_dev",eq=mbr)
         if not tableOnBootDisk: