Currently calling clean.sh leads to NEUTRON_LBAAS_DASHBOARD_ENABLE_FILE
being deleted. The problem is that this variable contains path to a
file in neutron-lbaas-dashboard directory, not its copy in Horizon
directory. This patch fixes this by deleting proper files.
Change-Id: I9fcb96e4a0928a2b6a9da3e70dbb0e185dff7108