bug #12572 [HttpFoundation] fix checkip6 (Neime)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #12572).

Discussion
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[HttpFoundation] fix checkip6

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

I have this error ContextErrorException: Warning: inet_pton(): Unrecognized address X.X.X.X:X
in IpUtils.php line 110

X.X.X.X:X is detected as a ipv6 because HTTP_X_FORWARDED_FOR have a port.

Commits
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1da0ba4 [Debug] fix checkip6

src/Symfony/Component/HttpFoundation/IpUtils.php

@@ -39,7 +39,7 @@ class IpUtils
             $ips = array($ips);
         }
 
-        $method = false !== strpos($requestIp, ':') ? 'checkIp6' : 'checkIp4';
+        $method = substr_count($requestIp, ':') > 1 ? 'checkIp6' : 'checkIp4';
 
         foreach ($ips as $ip) {
             if (self::$method($requestIp, $ip)) {