bitbake: xmlrpc: client - remove fatal errors

bitbake: xmlrpc: client - remove fatal errors

When we use the XMLRPC client API to connect to a bitbake server,
we want to receive errors from the API instead of having the
API exiting without warning.

Thus the "bb.fatal" calls have been replaced with "bb.warn" calls,
and we re-raise the original exception for handling by the
original caller.

The bitbake starting script has been modified to properly test
for failures in calling the client API and handle them.

Additional error handling added in the client, as to prevent
fatal crashes.

(Bitbake rev: eb63f08c33644f64752aaae2146a000956ce894a)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>