Fix regex for validating "remotehost" parameter

[Bischoff]

The regular expression used to validate "remotehost" parameter has two problems:

• the dots (.) should be escaped with \, otherwise they mean "any character" ;
• the second and further domain names are made of more than one character, and therefore need a +.

This small python program permits to reproduce the problem in isolation:

import re

rbad = '^[a-zA-Z0-9\-]+\@([0-9]{1,3}(.[0-9]{1,3}){3}$|[a-zA-Z0-9\-]+(.[a-zA-Z0-9\-]){1,}$)'
rok  = '^[a-zA-Z0-9\-]+\@([0-9]{1,3}(\.[0-9]{1,3}){3}$|[a-zA-Z0-9\-]+(\.[a-zA-Z0-9\-]+){1,}$)'
if re.compile(rbad).match("[email protected]") == None:
  print("failed")
else:
  print("matched")

Matching fails for [email protected], while this is a legitimate user@domain syntax. With the correct regular exception, it works.

Reference: https://cloudlib4zvm.readthedocs.io/en/latest/restapi.html#deploy-guest

the format is username@ip, for example, [email protected] or username@hostname eg.``[email protected]``

[Bischoff]

Thank you @bjhuangr .