Move to "github.com/hashicorp/go-hclog" (#4227)

* logbridge with hclog and identical output

* Initial search & replace

This compiles, but there is a fair amount of TODO
and commented out code, especially around the
plugin logclient/logserver code.

* strip logbridge

* fix majority of tests

* update logxi aliases

* WIP fixing tests

* more test fixes

* Update test to hclog

* Fix format

* Rename hclog -> log

* WIP making hclog and logxi love each other

* update logger_test.go

* clean up merged comments

* Replace RawLogger interface with a Logger

* Add some logger names

* Replace Trace with Debug

* update builtin logical logging patterns

* Fix build errors

* More log updates

* update log approach in command and builtin

* More log updates

* update helper, http, and logical directories

* Update loggers

* Log updates

* Update logging

* Update logging

* Update logging

* Update logging

* update logging in physical

* prefixing and lowercase

* Update logging

* Move phyisical logging name to server command

* Fix som tests

* address jims feedback so far

* incorporate brians feedback so far

* strip comments

* move vault.go to logging package

* update Debug to Trace

* Update go-plugin deps

* Update logging based on review comments

* Updates from review

* Unvendor logxi

* Remove null_logger.go

physical/spanner/spanner_test.go

@@ -5,9 +5,9 @@ import (
 	"testing"
 
 	"cloud.google.com/go/spanner"
-	"github.com/hashicorp/vault/helper/logformat"
+	log "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/vault/helper/logging"
 	"github.com/hashicorp/vault/physical"
-	log "github.com/mgutz/logxi/v1"
 	"golang.org/x/net/context"
 )
 
@@ -46,7 +46,7 @@ func TestBackend(t *testing.T) {
 		"database":   database,
 		"table":      table,
 		"ha_enabled": "false",
-	}, logformat.NewVaultLogger(log.LevelTrace))
+	}, logging.NewVaultLogger(log.Debug))
 	if err != nil {
 		t.Fatal(err)
 	}