Fix xen plugin to retry on upload failure

The xen plugin does not catch all cases where upload can throw
an exception due to connection failures and timeouts.  This
change extends the try/execpt window to catch these cases.

Also added original connect which in part keeps us from lazy-loading
the connection and logging of exception information so we can
figure out later what happened.

Change-Id: If643a7da9f602ab7bb5d255031a841c674fa6c6f
Fixes-bug: 1378903