Fix a bug that caused the services list to keep growing
Fix a bug that caused the services list to keep growing

This patch changes the code which looks up service and appends
them to the Exporter's list. It previously would create an
endless list and cause a memory leak.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <5f7133baa0f5c7ca63ff11e11f2e2b0d2cf077c8@gmail.com>

alexellis/faas,openfaas/faas,openfaas/faas,alexellis/faas,alexellis/faas,alexellis/faas,alexellis/faas,alexellis/faas,alexellis/faas,openfaas/faas,alexellis/faas,alexellis/faas