The LXC, QEMU, and LibXL drivers have all merged their handling of
the attach/update/modify device APIs into one large

  'xxxxDomainModifyDeviceFlags'

which then does a 'switch()' based on the actual API being invoked.
While this saves some lines of code, it is not really all that
significant in the context of the driver API impls as a whole.

This merger of the handling of different APIs creates pain when
wanting to automated analysis of the code and do things which
are specific to individual APIs. The slight duplication of code
from unmerged the API impls, is preferrable to allow for easier
automated analysis.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>