p2p: fix goroutine leak when handshake read fails
p2p: fix goroutine leak when handshake read fails

This regression was introduced in b3c058a9e4e9.

maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum