confd: services: only enable/disable or touch on actual changes

Previously svc_enadis() would call 'initctl enable + touch' for every
config change event, even when the service's enabled state was unchanged.
This caused rousette to be unnecessarily restarted on every test_reset(),
racing with the active RESTCONF connection on slow hardware.

Replace svc_enadis() and svc_change() with svc_enable() which only
manages nginx symlinks and calls 'initctl enable/disable' -- never touch.
Each handler now checks the diff for the specific leaf that changed:

- If /enabled appears in diff: call svc_enable() to start or stop it
- If other config leaves changed with service already enabled: touch only

This ensures rousette, ttyd, netbrowse, avahi, sshd, and lldpd are only
restarted when their configuration actually requires it.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/usr/libexec/infix/hostname

@@ -57,7 +57,6 @@ fi
 
 initctl -bq status lldpd && lldpcli configure system hostname "$new_hostname" 2>/dev/null
 initctl -bq touch mdns-alias 2>/dev/null
-initctl -bq touch netbrowse  2>/dev/null
 
 # If called from dhcp script we need to reload to activate new name in syslogd
 # Otherwise we're called from confd, which does the reload when all is done.