Update git submodules

* Update plugins/download-commands from branch 'master'
  to edd715618415d9a5e03b4555d9a2d3cca8fff6e8
  - Merge branch 'stable-2.15'
    
    * stable-2.15:
      Support an extra command for ssh command
    
    Change-Id: If2f68f9c83dae2faf038718d9ec94ba31587e330
    
  - Support an extra command for ssh command
    
    This would be useful to add an extra command like initializing submodules.
    
    Change-Id: If418279493e8556a8176a8b828c5edfc9f88e997
    
diff --git a/plugins/download-commands b/plugins/download-commands
index cf58d79..edd7156 160000
--- a/plugins/download-commands
+++ b/plugins/download-commands
@@ -1 +1 @@
-Subproject commit cf58d79bc034e8904aa459d8974df5796a734e1d
+Subproject commit edd715618415d9a5e03b4555d9a2d3cca8fff6e8