greybus: manifest: clean up properly when parsing cports

greybus: manifest: clean up properly when parsing cports

Currently, if an error occurs creating a connection, we simply
return an error without cleaning up any of the connections that
had already been successfully set up.

Add code to destroy connections that have been created in the event
an error occurs.  Add a check to ensure the bundle's list of
connections was empty before parsing for CPorts begins.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>