* qemud/driver.[ch], qemud/dispatch.c: fix the fact that
qemudDispatchDomainStart() doesn't report an error if the uuid
lookup fails and also move the uuid lookup into the driver
so that it matches the way we do Destroy().
* include/libvirt/libvirt.h.in, src/libvirt.c: add
virNetworkGetBridgeName() to allow finding out what
bridge to connect to in order to join a network.
* src/driver.h: add networkGetBridgeName() to vtable.
* qemud/protocol.h: add the request and reply to
the qemud protocol.
* qemud/dispatch.c, qemud/driver.[ch]: handle them
here.
* src/qemu_internal.c: implement GetBridgeName()
in the qemu driver.
* src/libvirt_sym.version: add new symbol.