When shutting down blocksync, it is observed that the process can hang completely. A dump of running goroutines reveals that this is due to goroutines not listening on the correct shutdown signal. Namely, the `poolRoutine` goroutine does not wait on `pool.Quit`. The `poolRoutine` does not receive any other shutdown signal during `OnStop` becuase it must stop before the `r.closeCh` is closed. Currently the `poolRoutine` listens in the `closeCh` which will not close until the `poolRoutine` stops and calls `poolWG.Done()`.
This change also puts the `requestRoutine()` in the `OnStart` method to make it more visible since it does not rely on anything that is spawned in the `poolRoutine`.
```
goroutine 183 [semacquire]:
sync.runtime_Semacquire(0xc0000d3bd8)
runtime/sema.go:56 +0x45
sync.(*WaitGroup).Wait(0xc0000d3bd0)
sync/waitgroup.go:130 +0x65
github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).OnStop(0xc0000d3a00)
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:193 +0x47
github.com/tendermint/tendermint/libs/service.(*BaseService).Stop(0xc0000d3a00, 0x0, 0x0)
github.com/tendermint/tendermint/libs/service/service.go:171 +0x323
github.com/tendermint/tendermint/node.(*nodeImpl).OnStop(0xc00052c000)
github.com/tendermint/tendermint/node/node.go:758 +0xc62
github.com/tendermint/tendermint/libs/service.(*BaseService).Stop(0xc00052c000, 0x0, 0x0)
github.com/tendermint/tendermint/libs/service/service.go:171 +0x323
github.com/tendermint/tendermint/cmd/tendermint/commands.NewRunNodeCmd.func1.1()
github.com/tendermint/tendermint/cmd/tendermint/commands/run_node.go:143 +0x62
github.com/tendermint/tendermint/libs/os.TrapSignal.func1(0xc000df6d20, 0x7f04a68da900, 0xc0004a8930, 0xc0005a72d8)
github.com/tendermint/tendermint/libs/os/os.go:26 +0x102
created by github.com/tendermint/tendermint/libs/os.TrapSignal
github.com/tendermint/tendermint/libs/os/os.go:22 +0xe6
goroutine 161 [select]:
github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).poolRoutine(0xc0000d3a00, 0x0)
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:464 +0x2b3
created by github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).OnStart
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:174 +0xf1
goroutine 162 [select]:
github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).processBlockSyncCh(0xc0000d3a00)
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:310 +0x151
created by github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).OnStart
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:177 +0x54
goroutine 163 [select]:
github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).processPeerUpdates(0xc0000d3a00)
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:363 +0x12b
created by github.com/tendermint/tendermint/internal/blocksync/v0.(*Reactor).OnStart
github.com/tendermint/tendermint/internal/blocksync/v0/reactor.go:178 +0x76
```