Pass these in because the defaults in docker.mk are lost
Pass these in because the defaults in docker.mk are lost

Travis otherwise runs SHARD= SHARDS=
causing this line
docker.test.shard: $(foreach image,$(shell echo $(images) | python util/balancecontainers.py $(SHARDS) | awk 'NR%$(SHARDS)==$(SHARD)'),$(docker_test)$(image))

to error with

```
awk: cmd. line:1: NR%==
awk: cmd. line:1:     ^ syntax error
usage: balancecontainers.py [-h] num_shards
balancecontainers.py: error: too few arguments
awk: cmd. line:1: NR%==
awk: cmd. line:1:     ^ syntax error
usage: balancecontainers.py [-h] num_shards
```

rue89-tech/configuration,proversity-org/configuration,edx/configuration,michaelsteiner19/open-edx-configuration,stvstnfrd/configuration,proversity-org/configuration,Stanford-Online/configuration,hks-epod/configuration,EDUlib/configuration,Stanford-Online/configuration,arbrandes/edx-configuration,arbrandes/edx-configuration,gsehub/configuration,proversity-org/configuration,stvstnfrd/configuration,hks-epod/configuration,EDUlib/configuration,michaelsteiner19/open-edx-configuration,gsehub/configuration,hks-epod/configuration,rue89-tech/configuration,appsembler/configuration,arbrandes/edx-configuration,hastexo/edx-configuration,hks-epod/configuration,stvstnfrd/configuration,hastexo/edx-configuration,mitodl/configuration,edx/configuration,appsembler/configuration,stvstnfrd/configuration,stvstnfrd/configuration,Stanford-Online/configuration,edx/configuration,Stanford-Online/configuration,proversity-org/configuration,mitodl/configuration,rue89-tech/configuration,appsembler/configuration,gsehub/configuration,rue89-tech/configuration,michaelsteiner19/open-edx-configuration,arbrandes/edx-configuration,EDUlib/configuration,hastexo/edx-configuration,edx/configuration,EDUlib/configuration,appsembler/configuration,rue89-tech/configuration,hastexo/edx-configuration,michaelsteiner19/open-edx-configuration,mitodl/configuration,arbrandes/edx-configuration,Stanford-Online/configuration,hks-epod/configuration,proversity-org/configuration,gsehub/configuration,hastexo/edx-configuration,mitodl/configuration,gsehub/configuration,EDUlib/configuration