ofproto-dpif: Initialize tunnel metadata in both 'flow' and 'base_flow'.

ofproto-dpif: Initialize tunnel metadata in both 'flow' and 'base_flow'.

The datapath doesn't carry over tunnel metadata between input and
output because such an operation doesn't generally make sense.  In
order to keep the flow information in sync, userspace needs to do
this as well.  However, userspace was clearing out only the base
flow, which means that it later generated an action with the original
tunnel metadata.  If a packet is both being sent and received on a
tunnel then this will cause the output tunnel's configuration to be
overriden with incorrect information.  This was recently exposed
when the ability to interpret tunnel metadata was added to userspace.

Reported-by: Anand Krishnamurthy <krishnamurt4@wisc.edu>
Reported-by: Saul St. John <sstjohn@cs.wisc.edu>
Signed-off-by: Jesse Gross <jesse@nicira.com>