When the logged-in user can't get to the member listing for a group
(bug #845287, bug #504830), it seems like a good idea to also hide
the number of members.

Member counts are hidden in the group info block and copy a view page
by moving member & view counting into the group_get_groupinfo_data
function, and performing the permission check in one place for both
pages.

Member counts are hidden on My Groups and Find Groups inside the
group_prepare_usergroups_for_display function.

Change-Id: Ibe5675861040cedf67c2ddff7647117cd155722a
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>