Correct kubectl-mongodb path for command prepare_local_e2e (#315)

# Summary

When we change the directory of `kubectl-mongodb` from
`public/tools/multicluster` to `cmd/kubectl-mongodb` we change the
source file `build_multi_cluster_kubeconfig_creator.sh` to use the new
path but I missed updating the new path in the file
`funcs/multicluster`. This PR fixes that problem and updates the path to
point to the correct location.

## Proof of Work

Run `make prepare_local_e2e`, that will build the `kubectl-mongodb`
binary and use the `kubectl mongodb multicluster` command to setup the
multicluster environment.

Author: viveksinghggits

scripts/funcs/multicluster

@@ -210,13 +210,13 @@ prepare_multi_cluster_e2e_run() {
     fi
 
     (
-      cd public/tools/multicluster/
+      cd cmd/kubectl-mongodb
       GOOS=darwin GOARCH="${goarch}" go build -o "${MULTI_CLUSTER_KUBE_CONFIG_CREATOR_PATH}" main.go
     )
     PATH=${PATH}:docker/mongodb-kubernetes-tests
   else
     (
-      cd public/tools/multicluster/
+      cd cmd/kubectl-mongodb
       # shellcheck disable=SC2030
       export PATH=${GOROOT}:${PATH}
       GOOS=linux GOARCH=amd64 go build -o "${MULTI_CLUSTER_KUBE_CONFIG_CREATOR_PATH}" main.go