TTP now builds with an empty local .m2 repo

Fixes bug 1656. For whatever reason, the ${nexusproxy} was not being expanded
appropriately in the opendaylight-snapshot repository block of the pom file.
This resulted in builds to an empty repo being unable to locate the odlparent
pom file. This fixes it by hard coding the value to the current nexus.

Change-Id: Ie5e801fe25b4059a2c5d2f0292c09d731c0bc872
Signed-off-by: Colin Dixon <colin@colindixon.com>