[Xend] Do network startup earlier.

[Xend] Do network startup earlier.

Xend tries to rebuild the network configuration such as bridges and
vlan interfaces  (in those bridges) when starting. Unfortunately this
fails on the first startup since the network script has not run, yet,
and for example created peth0. When restarting xend it works due to
the peth0 being there then. This patch moves the initialization of the
network to an earlier time in the xend initialization process to
mitigate this problem.

Signed-off-by: Stefan Berger <stefanb@us.ibm.com>