[pgAdmin4][Patch]: Background process executor won't run(in case of Backup, restore) in Windows only

Hi

While working on RM1391 I found another issue 'Backup is not working on windows".

The reason is that the process executor which uses subprocess Popen() to execute job fails when we pass close_fds=True and shell=False in windows.

Now we are settings close_fds=False and shell=True to fix it. These settings are specific to windows only.

Please review the attached patch.

Thanks,

Surinder Kumar