xenstat: Fixes for 20528:
e6e3bf767d16 (stats for dom0 network bonding)
In above c/s I introduced dom0 statistics for case we use network
bonding. The indentation was not good for xenstat C codebase and also
some modifications were done to the logic, mainly not using the parsed
variables we don't care about (as we care only about
{tx|rx}{bytes,packets,errs,drops} and no other variable from
/proc/net/dev) by passing NULLs to variables we don't care about. Also
dom0 statistics alteration was fixed to include {tx|rx}{drop,errs} for
dom0 (previous version of my patch was not having this code applied).
Signed-off-by: Michal Novotny <minovotn@redhat.com>