fix: set peerset size

addresses https://github.com/jbenet/go-ipfs/pull/438#discussion_r21952271

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

util/peerset/peerset.go

@@ -22,7 +22,7 @@ func NewPeerSet() *PeerSet {
 func NewLimitedPeerSet(size int) *PeerSet {
 	ps := new(PeerSet)
 	ps.ps = make(map[string]bool)
-	ps.size = -1
+	ps.size = size
 	return ps
 }