test: fix incorrect perf measurement

Added calls of b.ResetTimer() to all Benchmark tests before bench loop.
That call clears all counters of allocs, timers etc.
The preparation before bench loop affected perf results.

Follows up #122

Author: vr009

tarantool_test.go

@@ -81,6 +81,7 @@ func BenchmarkClientSerial(b *testing.B) {
 		b.Errorf("No connection available")
 	}
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		_, err = conn.Select(spaceNo, indexNo, 0, 1, IterEq, []interface{}{uint(1111)})
 		if err != nil {
@@ -105,6 +106,7 @@ func BenchmarkClientSerialTyped(b *testing.B) {
 	}
 
 	var r []Tuple
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		err = conn.SelectTyped(spaceNo, indexNo, 0, 1, IterEq, IntKey{1111}, &r)
 		if err != nil {
@@ -128,6 +130,7 @@ func BenchmarkClientFuture(b *testing.B) {
 		b.Error(err)
 	}
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i += N {
 		var fs [N]*Future
 		for j := 0; j < N; j++ {
@@ -158,6 +161,7 @@ func BenchmarkClientFutureTyped(b *testing.B) {
 		b.Errorf("No connection available")
 	}
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i += N {
 		var fs [N]*Future
 		for j := 0; j < N; j++ {
@@ -191,6 +195,7 @@ func BenchmarkClientFutureParallel(b *testing.B) {
 		b.Errorf("No connection available")
 	}
 
+	b.ResetTimer()
 	b.RunParallel(func(pb *testing.PB) {
 		exit := false
 		for !exit {
@@ -227,6 +232,7 @@ func BenchmarkClientFutureParallelTyped(b *testing.B) {
 		b.Errorf("No connection available")
 	}
 
+	b.ResetTimer()
 	b.RunParallel(func(pb *testing.PB) {
 		exit := false
 		for !exit {
@@ -266,6 +272,7 @@ func BenchmarkClientParallel(b *testing.B) {
 		b.Errorf("No connection available")
 	}
 
+	b.ResetTimer()
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			_, err := conn.Select(spaceNo, indexNo, 0, 1, IterEq, []interface{}{uint(1111)})
@@ -307,6 +314,8 @@ func BenchmarkClientParallelMassive(b *testing.B) {
 			}
 		}()
 	}
+
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		wg.Add(1)
 		limit <- struct{}{}
@@ -344,6 +353,8 @@ func BenchmarkClientParallelMassiveUntyped(b *testing.B) {
 			}
 		}()
 	}
+
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		wg.Add(1)
 		limit <- struct{}{}