Rename tests to help tctest.

Acceptance test output:

% go test -v ./aws/internal/net
=== RUN   TestCIDRBlocksEqual
--- PASS: TestCIDRBlocksEqual (0.00s)
=== RUN   TestCanonicalCIDRBlock
--- PASS: TestCanonicalCIDRBlock (0.00s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws/internal/net	0.687s

aws/internal/net/cidr_test.go

@@ -1,10 +1,12 @@
-package net
+package net_test
 
 import (
 	"testing"
+
+	tfnet "github.com/terraform-providers/terraform-provider-aws/aws/internal/net"
 )
 
-func Test_CIDRBlocksEqual(t *testing.T) {
+func TestCIDRBlocksEqual(t *testing.T) {
 	for _, ts := range []struct {
 		cidr1 string
 		cidr2 string
@@ -18,14 +20,14 @@ func Test_CIDRBlocksEqual(t *testing.T) {
 		{"::/0", "::0/0", true},
 		{"", "", false},
 	} {
-		equal := CIDRBlocksEqual(ts.cidr1, ts.cidr2)
+		equal := tfnet.CIDRBlocksEqual(ts.cidr1, ts.cidr2)
 		if ts.equal != equal {
 			t.Fatalf("CIDRBlocksEqual(%q, %q) should be: %t", ts.cidr1, ts.cidr2, ts.equal)
 		}
 	}
 }
 
-func Test_CanonicalCIDRBlock(t *testing.T) {
+func TestCanonicalCIDRBlock(t *testing.T) {
 	for _, ts := range []struct {
 		cidr     string
 		expected string
@@ -35,7 +37,7 @@ func Test_CanonicalCIDRBlock(t *testing.T) {
 		{"::0/0", "::/0"},
 		{"", ""},
 	} {
-		got := CanonicalCIDRBlock(ts.cidr)
+		got := tfnet.CanonicalCIDRBlock(ts.cidr)
 		if ts.expected != got {
 			t.Fatalf("CanonicalCIDRBlock(%q) should be: %q, got: %q", ts.cidr, ts.expected, got)
 		}