Add sleep before/after retrieving timestamp in the user guide.

Adding a sleep before was necessary since only adding a sleep after did not always work. This helps to ensure the backup stop time for the previous backup does not equal time-recovery-timestamp. The sleep after allows enough time between the time retrieval and dropping important_table so PostgreSQL can consistently recover to before the table drop.

Note that these issues were caused by picking a timestamp too close to the restore command or a database operation, not due to any problem in backup selection of the restore command.

doc/xml/user-guide.xml

@@ -1854,11 +1854,19 @@
         <execute-list host="{[host-pg1]}">
             <title>Get the time from <postgres/></title>
 
+            <execute user="postgres" show="n">
+                <exe-cmd>sleep 1</exe-cmd>
+            </execute>
+
             <execute user="postgres" output="y" filter="n" variable-key="time-recovery-timestamp">
                 <exe-cmd>
                     psql -Atc "select current_timestamp"
                 </exe-cmd>
             </execute>
+
+            <execute user="postgres" show="n">
+                <exe-cmd>sleep 1</exe-cmd>
+            </execute>
         </execute-list>
 
         <p>Now that the time has been recorded the table is dropped.  In practice finding the exact time that the table was dropped is a lot harder than in this example.  It may not be possible to find the exact time, but some forensic work should be able to get you close.</p>