tests: Do not pick an ip address that overlaps with ourselves

tests: Do not pick an ip address that overlaps with ourselves

The ospf_basic_functionality/test_ospf_lan.py creates
a ethernet segment and attaches 4 routers to it and
assigns ip addresses in a /24.  As one of the tests
it picks a new address for r0 which coincides with
a ip address on r3.  Then the test immediatly
checks for other data.  The problem is of course
that if a test is `slow` enough hello's will
start to be ignored from r3 to r0 and the
neighbor relationships will come down.  Choose
an ip address that doesn't cause this issue.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>