Document the need to restart Phabricator after performing a restore

Summary:
Depending on how you perform a restore, APC (or, e.g., running daemon processes) might be poisoned with out-of-date caches.

Add a note to advise installs to restart after restoring data.

See also lengthy fishing expedition support thread.

Test Plan: Read the text.

Reviewers: chad, amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18180

Author: epriestley

src/docs/user/configuration/configuring_backups.diviner

@@ -24,6 +24,12 @@ same steps you would if you were creating a backup and then restoring it, you
 will just backup the old machine and then restore the data onto the new
 machine.
 
+WARNING: You need to restart Phabricator after restoring data.
+
+Restarting Phabricator after performing a restore makes sure that caches are
+flushed properly. For complete instructions, see
+@{article:Restarting Phabricator}.
+
 
 Backup: MySQL Databases
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