Remove stickiness config from traefik backends

This config line prevents the downloaded binary version
of traefik from starting up, which in turn prevents the skydive
binary from starting up correctly.

Change-Id: Ic07a3c6170ff4e0ad60dbdb860eff0f330b677a1

skydive/roles/traefik_common/templates/traefik.toml.j2

@@ -57,7 +57,6 @@ watch = true
   {% for key, value in traefik_destinations.items() %}
     [backends.{{ key }}]
   {%   for server in value.servers %}
-      [backends.{{ key }}.loadbalancer.stickiness]
       [backends.{{ key }}.servers.{{ server.name }}]
       url = "{{ server.proto | default(value.proto) }}://{{ server.address }}:{{ server.port | default(value.port) }}"
       weight = {{ server.weight | default(100)  }}