zoneconf.cgi: Make output HTML 5 standard compliant
This fixes two minor violations of the HTML standard:
- <a> elements may not contain nested <button> elements:
Replace the button with a simple hyperlink, because it was only used as a link anyway.
- "id" attributes may not contain whitespace:
Remove unneeded attribute, use hyphens instead of spaces.
Signed-off-by: Leo-Andres Hofmann <hofmann@leo-andres.de> Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>