nat: change nat44-ed test pool address

nat: change nat44-ed test pool address

NAT pool address overlaps with pg4 network 10.0.0.1/24
this is not desirable because of upcoming change [1]. This
change uncovered configuration issue with hairpinning test
that would fail because of already configured pg4 interface
that  shares subnet with nat pool address. Packets would
incorectly end up in bad pg interface causing the test to fail.

This patch changes nat pool address to 10.0.10.3 that doesn't
belong to any of the subnets configured on pg interfaces in nat
tests.

[1] https://gerrit.fd.io/r/c/vpp/+/34441

Type: test

Change-Id: I49e63dacbf0847116adbcf1954ff5defd833a657
Signed-off-by: Filip Varga <fivarga@cisco.com>