Skip slow tests on (very) slow test targets.

.github/configs

@@ -145,6 +145,12 @@ case "$config" in
 esac
 
 case "${TARGET_HOST}" in
+    aix*)
+	# These are slow real or virtual machines so skip the slowest tests
+	# (which tend to be thw ones that transfer lots of data) so that the
+	# test run does not time out.
+	SKIP_LTESTS="rekey sftp"
+	;;
     dfly58*|dfly60*)
 	# scp 3-way connection hangs on these so skip until sorted.
 	SKIP_LTESTS=scp3