Tidy up misc. XHTML

"diag_dns.php"
Tidy up "equals sign"

"services_captiveportal.php"
Add space to OPTION tag
Update HTML Boolean operator
Close INPUT and BR tags

"services_captiveportal_hostname.php"
Update ALIGN to MIDDLE

"services_captiveportal_vouchers.php"
Move closing TD tag outside the PHP IF statement

"system_crlmanager.php"
Close TR tags correctly