Actually support unsafe logging.

Obfs4proxy implements the -unsafeLogging switch but it's been ignored so
far.  This patch makes it work.

ChangeLog

@@ -1,6 +1,7 @@
 Changes in version 0.0.12 - UNRELEASED:
  - Replace the extra25519 import with an internal package.
  - Update the Azure TLS certificate digest (Thanks to Philipp Winter).
+ - Make the -unsafeLogging command line switch work.
 
 Changes in version 0.0.11 - 2019-06-21:
  - Update my e-mail address.

common/log/log.go

@@ -70,6 +70,7 @@ func Init(enable bool, logFilePath string, unsafe bool) error {
 		log.SetOutput(ioutil.Discard)
 	}
 	enableLogging = enable
+	unsafeLogging = unsafe
 	return nil
 }