Test fix for hostpool package

hostpool package test was refactored to create HostInfo via exported NewhostInfo() constructor.
NewHostInfo() was exposed.

patch by Oleksandr Luzhniy; for CASSGO-59

Author: tengu-alt

conn.go

@@ -1690,7 +1690,7 @@ func (c *Conn) awaitSchemaAgreement(ctx context.Context) (err error) {
 		}
 
 		for _, row := range rows {
-			h, err := newHostInfo(c.host.ConnectAddress(), c.session.cfg.Port)
+			h, err := NewHostInfo(c.host.ConnectAddress(), c.session.cfg.Port)
 			if err != nil {
 				goto cont
 			}

control.go

@@ -146,7 +146,7 @@ func hostInfo(addr string, defaultPort int) ([]*HostInfo, error) {
 
 	// Check if host is a literal IP address
 	if ip := net.ParseIP(host); ip != nil {
-		h, err := newHostInfo(ip, port)
+		h, err := NewHostInfo(ip, port)
 		if err != nil {
 			return nil, err
 		}
@@ -176,7 +176,7 @@ func hostInfo(addr string, defaultPort int) ([]*HostInfo, error) {
 	}
 
 	for _, ip := range ips {
-		h, err := newHostInfo(ip, port)
+		h, err := NewHostInfo(ip, port)
 		if err != nil {
 			return nil, err
 		}

host_source.go

@@ -181,7 +181,9 @@ type HostInfo struct {
 	tokens           []string
 }
 
-func newHostInfo(addr net.IP, port int) (*HostInfo, error) {
+// NewHostInfo creates HostInfo with provided connectAddress and port.
+// It returns an error if addr is invalid.
+func NewHostInfo(addr net.IP, port int) (*HostInfo, error) {
 	if !validIpAddr(addr) {
 		return nil, errors.New("invalid host address")
 	}

hostpool/hostpool_test.go

@@ -17,12 +17,18 @@ func TestHostPolicy_HostPool(t *testing.T) {
 	//	{hostId: "0", connectAddress: net.IPv4(10, 0, 0, 0)},
 	//	{hostId: "1", connectAddress: net.IPv4(10, 0, 0, 1)},
 	//}
-	firstHost := &gocql.HostInfo{}
+	
+	firstHost, err := gocql.NewHostInfo(net.IPv4(10, 0, 0, 0), 9042)
+	if err != nil {
+		t.Errorf("Error creating first host: %v", err)
+	}
 	firstHost.SetHostID("0")
-	firstHost.SetConnectAddress(net.IPv4(10, 0, 0, 0))
-	secHost := &gocql.HostInfo{}
+
+	secHost, err := gocql.NewHostInfo(net.IPv4(10, 0, 0, 1), 9042)
+	if err != nil {
+		t.Errorf("Error creating second host: %v", err)
+	}
 	secHost.SetHostID("1")
-	secHost.SetConnectAddress(net.IPv4(10, 0, 0, 1))
 	hosts := []*gocql.HostInfo{firstHost, secHost}
 	// Using set host to control the ordering of the hosts as calling "AddHost" iterates the map
 	// which will result in an unpredictable ordering