systemd: allow nfd-status-http-server to bind to any port

Change-Id: Ie6e2af3b2e194fbe0c4952b90fc39844b20722f0
Refs: #4533
diff --git a/systemd/nfd-status-http-server.service.in b/systemd/nfd-status-http-server.service.in
index fa1469b..95a0563 100644
--- a/systemd/nfd-status-http-server.service.in
+++ b/systemd/nfd-status-http-server.service.in
@@ -31,14 +31,15 @@
 ExecStart=@BINDIR@/nfd-status-http-server $FLAGS
 Restart=on-failure
 RestartPreventExitStatus=2
+User=ndn
 
+AmbientCapabilities=CAP_NET_BIND_SERVICE
 CapabilityBoundingSet=CAP_NET_BIND_SERVICE
 LockPersonality=yes
 MemoryDenyWriteExecute=yes
 NoNewPrivileges=yes
 PrivateDevices=yes
 PrivateTmp=yes
-PrivateUsers=yes
 ProtectControlGroups=yes
 ProtectHome=yes
 ProtectKernelModules=yes