SimpleConfigReader: add IP address lookup helpers
SimpleConfigReader: add IP address lookup helpers

Add the following functions to SimpleConfigReader:
GetInstanceByIp, nic ip -> instance name
GetNodePrimaryIp, node name -> node primary ip
GetInstancePrimaryNode, instance name -> primary node

For the first one we precalculate the _ip_to_instance, so we don't have
to loop over all instances for each query.

Signed-off-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

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