Bug 28597: Fetch the logged in branchcode for OpacSuggestioninstructions

Bug 28597: Fetch the logged in branchcode for OpacSuggestioninstructions

To test:
 1 - Set two news items with location 'OpacSuggestioninstructions'
 2 - One should be for all libraries
 3 - One should be for a specific library
 4 - Sign in to opac with user from the specific library
 5 - Add a suggestion
 6 - The instructions only show the all libraries item
 7 - Apply patch
 8 - Reload
 9 - All libraries and specific library items are shown
10 - Allow anonymous suggestions:  AnonSuggestions - Allow
11 - Sign out of opac
12 - Add a suggestion
13 - Only all librares news is visible

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>