lxc-oracle: export upstart environment variable for maygetty

This is a fix to commit 5f2ea8cfcb8ccd9bbb7cf18e1e260044f3f6dcaf.
Sorry, not sure how I missed this in testing the original patch.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>