[php-src] Issue #20981: sni_server.phpt fails half the time

Issue: https://github.com/php/php-src/issues/20981
Author: ndossche

### Description

```
========DIFF========
     string(%d) "cs.php.net"
002- string(%d) "uk.php.net"
003- string(%d) "us.php.net"
002+ 
003+ Warning: Undefined array key "peer_certificate" in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 16
004+ 
005+ Deprecated: openssl_x509_parse(): Passing null to parameter #1 ($certificate) of type OpenSSLCertificate|string is deprecated in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 17
006+ 
007+ Warning: Trying to access array offset on false in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 17
008+ 
009+ Warning: Trying to access array offset on null in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 17
010+ NULL
011+ 
012+ Warning: Undefined array key "peer_certificate" in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 22
013+ 
014+ Deprecated: openssl_x509_parse(): Passing null to parameter #1 ($certificate) of type OpenSSLCertificate|string is deprecated in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 23
015+ 
016+ Warning: Trying to access array offset on false in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 23
017+ 
018+ Warning: Trying to access array offset on null in /work/php-src/ext/openssl/tests/ServerClientTestCase.inc(191) : eval()'d code on line 23
019+ NULL
========DONE========
FAIL sni_server [/work/php-src/ext/openssl/tests/sni_server.phpt] 
```

### PHP Version

```plain
master
```

### Operating System

Ubuntu 24.04