CLOUDSTACK-6438, CLOUDSTACK-6442: XAPI plugins must be copied to XS master first

Backported fix for 4.3 using e0e226869d83189dcdb69e3c18b24c47e2b8f1fe by:
Anthony Xu <anthony.xu@citrix.com>

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>