netkwork/hive: addPeer function assigned after launching goroutine co…

[kortatu]

At hive Start() we launch the loadPeers and inside it we launch the goroutine go h.connectInitialPeers(conns). After that addPeer is assigned, this resulted that in some test executions, the connection to the peers is done before the function is set.
We have moved the assign before the loadPeers call.

Previous error

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xb07f2d]

goroutine 31931 [running]:
github.com/ethersphere/swarm/network.(*Hive).connectInitialPeers(0xc00fa226e0, 0xc0148ed880, 0xd, 0xd)
    /home/rinke/go/src/github.com/ethersphere/swarm/network/hive.go:284 +0x5cd
created by github.com/ethersphere/swarm/network.(*Hive).loadPeers
    /home/rinke/go/src/github.com/ethersphere/swarm/network/hive.go:269 +0x59b
FAIL    github.com/ethersphere/swarm/network/simulations/discovery    14.576s