Fix kickstart --dhcpclass option application

[rvykydal]

Port of upstream fix #5563 which didn't make it into rhel10.

[pep8speaks]

Hello @rvykydal! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file tests/unit_tests/pyanaconda_tests/modules/network/test_module_network_nm_client.py:

Line 692:100: E501 line too long (104 > 99 characters)
Line 713:100: E501 line too long (102 > 99 characters)
Line 737:100: E501 line too long (102 > 99 characters)
Line 758:100: E501 line too long (102 > 99 characters)
Line 782:100: E501 line too long (102 > 99 characters)
Line 804:100: E501 line too long (102 > 99 characters)
Line 825:100: E501 line too long (102 > 99 characters)
Line 848:100: E501 line too long (102 > 99 characters)
Line 872:100: E501 line too long (102 > 99 characters)
Line 896:100: E501 line too long (102 > 99 characters)
Line 933:100: E501 line too long (102 > 99 characters)

[rvykydal]

We need also to update related kickstart test in a way similar to rhinstaller/kickstart-tests#1206

[rvykydal]

/kickstar-test --testtype smoke

[rvykydal]

/kickstart-test --testtype smoke

[M4rtinK]

Looks good to me. :)

[jkonecny12]

LGTM!