Fix trimming on the docker-gen template

Incorrect trimming did lead to empty domains being created on space separated domains
or with comma trailed LETSENCRYPT_HOST environment variable. This in turns led to the
container being caught in an endless loop trying to delete /etc/nginx/certs nginx-proxy#254 nginx-proxy#288

Author: buchdag

app/letsencrypt_service_data.tmpl

@@ -2,15 +2,13 @@ LETSENCRYPT_CONTAINERS=({{ range $hosts, $containers := groupBy $ "Env.LETSENCRY
 
 {{ range $hosts, $containers := groupBy $ "Env.LETSENCRYPT_HOST" }}
 
-{{ if trim $hosts }}
+{{ $hosts := trimSuffix "," $hosts }}
 
 {{ range $container := $containers }}{{ $cid := printf "%.12s" $container.ID }}
-LETSENCRYPT_{{ $cid }}_HOST=( {{ range $host := split $hosts "," }}'{{ $host }}' {{ end }})
+LETSENCRYPT_{{ $cid }}_HOST=( {{ range $host := split $hosts "," }}{{ $host := trim $host }}'{{ $host }}' {{ end }})
 LETSENCRYPT_{{ $cid }}_EMAIL="{{ $container.Env.LETSENCRYPT_EMAIL }}"
 LETSENCRYPT_{{ $cid }}_KEYSIZE="{{ $container.Env.LETSENCRYPT_KEYSIZE }}"
 LETSENCRYPT_{{ $cid }}_TEST="{{ $container.Env.LETSENCRYPT_TEST }}"
 {{ end }}
 
 {{ end }}
-
-{{ end }}