Fix test race condition

[arnaud-lb]

There is a race condition in https://github.com/php/php-src/blob/ec277ce7fe1e7b7f98e270198826fc1432cdcb3d/ext/openssl/tests/gh13860.phpt: If the first fread($fp, 2); (line 36) is executed after fwrite($client, "xx");, the test hangs indefinitely in the loop: https://github.com/php/php-src/blob/ec277ce7fe1e7b7f98e270198826fc1432cdcb3d/ext/openssl/tests/gh13860.phpt#L39C1-L41C6

I've observed this on Alpine with a ZTS + ASAN build, in #13925, but adding a sleep() before the first fread() will also reproduce the issue.

Moving the phpt_wait() before fwrite() fixes the hang by ensuring that fread($fp, 2); executes before fwrite(). However I'm not sure this is still testing the right thing (although the test fails if I revert 2aae14c).

[nielsdos]

Good catch, the modified test should catch the issue as well. Note that the test also exists on lower versions.