Correct errors on the Public Activity feed page
Correct errors on the Public Activity feed page

It turns out that destroying the old JoinRequest would break some
activities on the main page, causing them to say that the space
no longer exists. Now we simply mark the old JoinRequest as processed,
neither accepting nor declining it.

refs #1604

fbottin/mconf-web,mconf-ufrgs/mconf-web,mconf/mconf-web,mconftec/mconf-web-uergs,lfzawacki/mconf-web,mconftec/mconf-web-mytruecloud,mconftec/mconf-web-uergs,mconftec/mconf-web-santacasa,mconf-ufrgs/mconf-web,akratech/Akraconference,amreis/mconf-web,amreis/mconf-web,fbottin/mconf-web,fbottin/mconf-web,mconftec/mconf-web-santacasa,mconf-rnp/mconf-web,mconftec/mconf-web-santacasa,mconf/mconf-web,mconftec/mconf-web-uergs,mconftec/mconf-web-santacasa,fbottin/mconf-web,mconf-rnp/mconf-web,mconftec/mconf-web-mytruecloud,becueb/MconfWeb,akratech/Akraconference,lfzawacki/mconf-web,mconf-ufrgs/mconf-web,mconftec/mconf-web-mytruecloud,amreis/mconf-web,lfzawacki/mconf-web,mconf/mconf-web,amreis/mconf-web,akratech/Akraconference,mconftec/mconf-web-uergs,becueb/MconfWeb,mconf-rnp/mconf-web,mconf-ufrgs/mconf-web,becueb/MconfWeb,mconf-rnp/mconf-web,lfzawacki/mconf-web,becueb/MconfWeb,mconftec/mconf-web-mytruecloud,akratech/Akraconference,mconf/mconf-web