Remove reloads when there is no endpoints

[aledbf]

Which issue this PR fixes: fixes #3315

This PR removes the need to reload NGINX when there is a change in the number of endpoints (in particular 0).
Without this PR, when the replica count is 0 we had this

I1106 12:19:13.390606       6 nginx.go:629] NGINX configuration diff:
--- /etc/nginx/nginx.conf	2018-11-06 12:18:56.514692638 +0000
+++ /tmp/new-nginx-cfg561164329	2018-11-06 12:19:13.387865859 +0000
@@ -1,5 +1,5 @@
 
-# Configuration checksum: 14086898480532449296
+# Configuration checksum: 8624603592146078350
 
 # setup custom paths that do not require root access
 pid /tmp/nginx.pid;
@@ -533,7 +533,7 @@
 			
 			port_in_redirect off;
 			
-			set $proxy_upstream_name "default-http-svc-80";
+			set $proxy_upstream_name "";
 			
 			client_max_body_size                    1m;

which triggered the reload. With the introduced changes there is no difference in the configuration file

[ElvinEfendi]

we need to be careful with this since the payload includes private key as well in dynamic certificate mode

[aledbf]

removed. I added that temporarily to help to debug.

[ElvinEfendi]

This PR removes the need to reload NGINX when there is a change in the number of endpoints (in particular 0).

to be clear only when number of endpoints is 0.

[ElvinEfendi]

/lgtm

[k8s-ci-robot]

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