Revert "providers/docker: Container links are an array, not a hash"

This reverts commit b68cb6d7b4.

plugins/providers/docker/driver.rb

@@ -31,7 +31,7 @@ module VagrantPlugins
 
       def create(params, **opts, &block)
         image   = params.fetch(:image)
-        links   = Array(params.fetch(:links))
+        links   = params.fetch(:links)
         ports   = Array(params[:ports])
         volumes = Array(params[:volumes])
         name    = params.fetch(:name)
@@ -43,7 +43,7 @@ module VagrantPlugins
         run_cmd << "-d" if params[:detach]
         run_cmd += env.map { |k,v| ['-e', "#{k}=#{v}"] }
         run_cmd += expose.map { |p| ['--expose', "#{p}"] }
-        run_cmd += links.map { |l| ['--link', "#{l}"] }
+        run_cmd += links.map { |k, v| ['--link', "#{k}:#{v}"] }
         run_cmd += ports.map { |p| ['-p', p.to_s] }
         run_cmd += volumes.map { |v| ['-v', v.to_s] }
         run_cmd += %W(--privileged) if params[:privileged]