CP-15745: cp instead of git cloning

Travis only provides us with a thin clone of the repo, so git clone
doesn't work.

Signed-off-by: John Else <john.else@citrix.com>

Author: johnelse

travis/build-internal.sh

@@ -2,6 +2,6 @@
 
 set -eux
 
-git clone /repo/xen-api
+cp -r /repo/xen-api .
 cd xen-api
 ./configure && make && make test