Update CHANGELOG, fix tests

CHANGELOG.md

@@ -61,6 +61,7 @@ BUG FIXES:
   - synced\_folders/nfs: Acquires a process-level lock so exports don't
       collide with Vagrant running in parallel.
   - synced\_folders/rsync: Add UserKnownHostsFile option to not complain. [GH-3511]
+  - synced\_folders/rsync: Proxy command is used properly if set. [GH-3553]
 
 PLUGIN AUTHOR CHANGES:
 

plugins/synced_folders/rsync/helper.rb

@@ -56,7 +56,11 @@ module VagrantPlugins
         # Connection information
         username = ssh_info[:username]
         host     = ssh_info[:host]
-        proxy_command = "-o ProxyCommand='#{ssh_info[:proxy_command]}' " if ssh_info[:proxy_command]
+        proxy_command = ""
+        if ssh_info[:proxy_command]
+          proxy_command = "-o ProxyCommand='#{ssh_info[:proxy_command]}' "
+        end
+
         rsh = [
           "ssh -p #{ssh_info[:port]} " +
           proxy_command +