Check ssl_in_use flag when reporting statistics

Previously we checked that the ssl pointer was not null, but this puts a
requirement on there being such a pointer which may not be true in
future multi-ssl-library supporting times. This seems to have been an
oversight in 9029f4b374, but hasn't really had any effect since we only
have one library.

Author: Daniel Gustafsson

src/backend/postmaster/pgstat.c

@@ -2989,7 +2989,7 @@ pgstat_bestart(void)
 		MemSet(&lbeentry.st_clientaddr, 0, sizeof(lbeentry.st_clientaddr));
 
 #ifdef USE_SSL
-	if (MyProcPort && MyProcPort->ssl != NULL)
+	if (MyProcPort && MyProcPort->ssl_in_use)
 	{
 		lbeentry.st_ssl = true;
 		lsslstatus.ssl_bits = be_tls_get_cipher_bits(MyProcPort);