Fix potential environment variable deadlock

We have to unlock the environment before bailing out.

Author: cmb69

Diff for: ext/standard/basic_functions.c

@@ -4234,6 +4234,7 @@ PHP_FUNCTION(putenv)
 		}
 		/* valw may be NULL, but the failed conversion still needs to be checked. */
 		if (!keyw || !valw && value) {
+			tsrm_env_unlock();
 			efree(pe.putenv_string);
 			efree(pe.key);
 			free(keyw);