sshd: tag getpwclass wrapper is MON_ISAUTH not MON_AUTH

In r339216 a privsep wrapper was added for login_getpwclass to address
PR 231172.  Unfortunately the change used the MON_AUTH flag in the
wrapper, and MON_AUTH includes MON_AUTHDECIDE which triggers an
auth_log() on each invocation.  getpwclass() does not participate in the
authentication decision, so should be MON_ISAUTH instead.

PR:		234793
Submitted by:	Henry Hu

crypto/openssh/monitor.c

@@ -193,7 +193,7 @@ struct mon_table mon_dispatch_proto20[] = {
 #endif
     {MONITOR_REQ_SIGN, MON_ONCE, mm_answer_sign},
 #ifdef HAVE_LOGIN_CAP
-    {MONITOR_REQ_GETPWCLASS, MON_AUTH, mm_answer_login_getpwclass},
+    {MONITOR_REQ_GETPWCLASS, MON_ISAUTH, mm_answer_login_getpwclass},
 #endif
     {MONITOR_REQ_PWNAM, MON_ONCE, mm_answer_pwnamallow},
     {MONITOR_REQ_AUTHSERV, MON_ONCE, mm_answer_authserv},