dpkg-trigger: On --help print the default admindir

Instead of the one passed on the command line.

debian/changelog

@@ -13,6 +13,8 @@ dpkg (1.15.5) UNRELEASED; urgency=low
     finishing fatally.
   * Update md5 file paths in debian/copyright.
     Thanks to Jonathan Nieder <jrnieder@gmail.com>.
+  * On ‘dpkg-trigger --help’ print the default admindir instead of the one
+    passed on the command line.
 
   [ Raphaël Hertzog ]
   * Add versioned dependency on base-files (>= 5.0.0) to dpkg-dev to ensure

src/trigcmd.c

@@ -111,7 +111,7 @@ usage(void)
 "                                     by dpkg).\n"
 "  --no-await                       No package needs to await the processing.\n"
 "  --no-act                         Just test - don't actually change anything.\n"
-"\n"), admindir);
+"\n"), ADMINDIR);
 
 	m_output(stdout, _("<standard output>"));
 }