`lite` binary broken due to duplicate flag registration

[juliusv]

#712 caused ingester flags to be registered twice in the lite binary, which instantiates both an ingester and a distributor:

./cmd/lite/lite 
./cmd/lite/lite flag redefined: ingester.client.max-recv-message-size
panic: ./cmd/lite/lite flag redefined: ingester.client.max-recv-message-size

[juliusv]

@khaines

[juliusv]

This was fixed by @lelenanam in #760