invoice: don't convert local date into DateTime
invoice: don't convert local date into DateTime

All invoice dates are already in the account timezone - don't try to
convert them.

Signed-off-by: Pierre-Alexandre Meyer <ff019a5748a52b5641624af88a54a2f0e46a9fb5@ning.com>

killbill/killbill-admin-ui,sbrossie/killbill-admin-ui,ning/killbill-admin-ui,wwjbatista/killbill-admin-ui,wwjbatista/killbill-admin-ui,jaimerson/killbill-admin-ui,killbill/killbill-admin-ui,killbill/killbill-admin-ui,sbrossie/killbill-admin-ui,ning/killbill-admin-ui,jaimerson/killbill-admin-ui,wwjbatista/killbill-admin-ui,jaimerson/killbill-admin-ui,killbill/killbill-admin-ui