all: fix errors reported by vet, golint

None are "wrong" per se, but there are a lot of good suggestions and
in one case a docstring that was not present in godoc due to the
presence of an extra newline.

Changed "Id" in struct properties to "ID" in some non-exported
structs. Removed a trailing period from some error messages; I believe
the exact contents of error strings are not covered by the Go
compatibility promise.

Change-Id: I7c620582dc247396f72c52d38c909ccc0ec87b83
Reviewed-on: https://go-review.googlesource.com/80145
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

ssh/test/doc.go

@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This package contains integration tests for the
+// Package test contains integration tests for the
 // golang.org/x/crypto/ssh package.
 package test // import "golang.org/x/crypto/ssh/test"

ssh/test/test_unix_test.go

@@ -25,7 +25,7 @@ import (
 	"golang.org/x/crypto/ssh/testdata"
 )
 
-const sshd_config = `
+const sshdConfig = `
 Protocol 2
 Banner {{.Dir}}/banner
 HostKey {{.Dir}}/id_rsa
@@ -51,7 +51,7 @@ HostbasedAuthentication no
 PubkeyAcceptedKeyTypes=*
 `
 
-var configTmpl = template.Must(template.New("").Parse(sshd_config))
+var configTmpl = template.Must(template.New("").Parse(sshdConfig))
 
 type server struct {
 	t          *testing.T
@@ -271,7 +271,7 @@ func newServer(t *testing.T) *server {
 	}
 
 	var authkeys bytes.Buffer
-	for k, _ := range testdata.PEMBytes {
+	for k := range testdata.PEMBytes {
 		authkeys.Write(ssh.MarshalAuthorizedKey(testPublicKeys[k]))
 	}
 	writeFile(filepath.Join(dir, "authorized_keys"), authkeys.Bytes())