euca-bundle-image requires a new architecture parameter

Ran into this issue while trying to enable UCA. This switch was
documented by the euca2ools team in:
https://eucalyptus.atlassian.net/browse/DOC-807

Closes-Bug: #1304571

Change-Id: I1ea7c6a760c75e67f09e566d73e571be3a1d89ea
(cherry picked from commit 6066327474f9e4a9f3f6f3db11138f06c942ecb8)