Use proper DPDK EAL parameter name: --allow

Use proper DPDK EAL parameter name: --allow

The name of one of the EAL parameters has changed. Depending on the DPDK
version, we need to use a different name. While building the PROX image,
we need now to create a file /opt/rapid/dpdk_version that contains the
DPDK version. When running runrapid.py, we will now check this file to
decide if we use the old --whitelist, or the new --allow parameter name
for the PCI address to be used.

Signed-off-by: Luc Provoost <luc.provoost@gmail.com>
Change-Id: I3e07c552d014c818138d389abce936e275108776