Async export: Incoherence of UI for a user that tries to export while an identical export is already in progress for another user

see more details in https://jira.xwiki.org/browse/XALTXLS-23?focusedCommentId=105882&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-105882 .

To reproduce:

• start an export with a user, for a livetable for a given filter configuration and sort
• while this export is in progress, arrive on the page with another user
• try to export again with the same filters and sort as the first user
• the second user will get a message that an export is already being done, and will get acces to this export (will see the progress of this export)
  • at the end of this export, the second user will get a success message and a link to access the file

Expected result:

• clicking on the link to download the file works
  Actual result:
• upon clicking on the link, an error message is displayed as the second user cannot access the file produced by the first user - security feature implemented for XALTXLS-23 .

Actually, as a fix, the second user should not get access to the progress of the first user's export, this re-entry of the same export (if one is in progress) should be limited to the user that launched it. The export of the second user should be considered a different export than the first one (which it actually is, for rights reasons).