Add GetInstanceNetworks() config method
Add GetInstanceNetworks() config method

This will be needed for Instance Queries. It walks through the
instance's NICs and returns a list network uuids that the NICs
are attached to.

Signed-off-by: Dimitris Aragiorgis <4514117c4a99256e19437c7e3407c4ecbf98aec0@grnet.gr>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

bitemyapp/ganeti,grnet/snf-ganeti,leshchevds/ganeti,onponomarev/ganeti,andir/ganeti,apyrgio/ganeti,onponomarev/ganeti,yiannist/ganeti,ganeti/ganeti,andir/ganeti,leshchevds/ganeti,mbakke/ganeti,grnet/snf-ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,apyrgio/ganeti,ganeti-github-testing/ganeti-test-1,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,bitemyapp/ganeti,dimara/ganeti,yiannist/ganeti,andir/ganeti,apyrgio/snf-ganeti,ganeti/ganeti,mbakke/ganeti,ganeti/ganeti,dimara/ganeti,mbakke/ganeti