Bug 1721866: Don't show "multiple journals" blurb in group journal posts page

Also show correct 'No journals' message depending if we are looking at
group, site, or institution journal list page

behatnotneeded

Change-Id: I237b1ab417ac6c5b7fa26081d0ebfdf0f9b93e08
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
(cherry picked from commit 1a7c2a20)