[grpc] make more sybil commands friendly to repeated execution

[okayzed]

currently, the sybil binary is designed to run once and then exit - we need to audit and fix the individual areas so we can ingest, digest and query multiple times in the same sybil process.

this means that sybil funcs shouldn't have nasty side effects that modify global state.

[tmc]

#40 paves the way for parallelism in tests which will allow the race detector to surface issues that relate to this.

[okayzed]

at first, i was wondering how -race will help with global state, but now i realize that the test runner will be running simultaneous query, ingest and digest tests which will all be touching global state