Bug 20484: Allow configuration of ES before switching to ES

Bug 20484: Allow configuration of ES before switching to ES

To test:
1 - Set SearchEngine syspref to Zebra
2 - Be a user with permission to manage search engine configuration (manage_search_engine_config)
3 - Confirm you do not see 'Search engine configuration' on Admin main page
4 - Apply patch
5 - Confirm you see it with '(Elasticsearch)' appended
6 - Be a user without above permission
7 - Confirm you cannot see the 'Search engine configuration'
8 - Confirm you cannot access directly:
    /cgi-bin/koha/admin/searchengine/elasticsearch/mappings.pl

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>