Add "%I" (instance name) to application log formats

Summary:
Ref T12611. Currently, the HTTP/SSH logs don't have an option to include the instance name.

Add such an option.

Leave it out of the default logs because most installs don't use this.

Test Plan: See next changes.

Reviewers: chad, amckinley

Reviewed By: chad

Maniphest Tasks: T12611

Differential Revision: https://secure.phabricator.com/D17776

src/applications/config/option/PhabricatorAccessLogConfigOptions.php

@@ -35,6 +35,7 @@ final class PhabricatorAccessLogConfigOptions
       'P' => pht('The logged-in user PHID, if one is logged in.'),
       'i' => pht('Request input, in bytes.'),
       'o' => pht('Request output, in bytes.'),
+      'I' => pht('Cluster instance name, if configured.'),
     );
 
     $http_map = $common_map + array(

src/infrastructure/log/PhabricatorAccessLog.php

@@ -30,6 +30,7 @@ final class PhabricatorAccessLog extends Phobject {
             'h' => php_uname('n'),
             'p' => getmypid(),
             'e' => time(),
+            'I' => PhabricatorEnv::getEnvConfig('cluster.instance'),
           ));
 
       self::$log = $log;

src/infrastructure/log/PhabricatorSSHLog.php

@@ -20,6 +20,7 @@ final class PhabricatorSSHLog extends Phobject {
         'h' => php_uname('n'),
         'p' => getmypid(),
         'e' => time(),
+        'I' => PhabricatorEnv::getEnvConfig('cluster.instance'),
       );
 
       $sudo_user = PhabricatorEnv::getEnvConfig('phd.user');