ovs-test: Enhancements to the ovs-test tool

ovs-test: Enhancements to the ovs-test tool

-Implemented support for ovs-test client, so that it could automatically
spawn an ovs-test server process from itself. This reduces the number of
commands the user have to type to get tests running.
-Automated creation of OVS bridges and ports (for VLAN and GRE tests), so that
user would not need to invoke ovs-vsctl manually to switch from direct, 802.1Q
and GRE tests.
-Fixed some pylint reported warnings.
-Fixed ethtool invocation so that we always try to query the physical interface
to get the driver name and version.
-and some others enhancements.

The new usage:
Node1:ovs-test -s 15531
Node2:ovs-test -c 127.0.0.1,1.1.1.1 192.168.122.151,1.1.1.2 -d -l 125 -t gre

Signed-off-by: Ansis Atteka <aatteka@nicira.com>