Disable the JIRA reindex button

Atlassian's issue tracker JIRA maintains file based indexes to make looking up issues faster. Certain changes (such as adding or changes custom fields) will make JIRA prompt administrators to rebuild these indexes. Unfortunately, this process makes JIRA unaccessible until it is complete (up to 20 minutes for a medium sized instance on version 5, less on version 6). Version 6 added background reindexing, however my experience of this is that it takes hours and uses up nearly all the CPU on the server.