Bug 10647 - Make OPAC MARC plain view work for all flavours of MARC

On "MARC view" in the OPAC, clicking on "Plain view" does not work
for UNIMARC and NORMARC.

To test:
- Make sure you have a UNIMARC or NORMARC setup
- Go to the "MARC view" of a record in the OPAC
- Click on "view plain" and observe the "Sorry, plain view is
  temporarily unavailable." error message
- Apply the patch
- Click on "view plain" and observe that a plain view of the MARC
  record is now displayed
- Sign off

I have only tested this on NORMARC, it might be good if someone
can test on UNIMARC.

Updated 2014-03-13: Incoroprates changes suggested by Marcel.
Test plan is the same as before.

Updated 2014-03-13: Tested in my UNIMARC system.
toggled opactheme to all three values, with OPACXSLTDetailsDisplay
and OPACXSLTResultsDisplay both set to default.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Tested with MARC21 and UNIMARC, passes all tests and QA script.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit b4f5fee48c)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

opac/opac-showmarc.pl

@@ -71,7 +71,7 @@ if ($view eq 'card' || $view eq 'html') {
         $xslfile = "compact.xsl";
     }
     else { # must be html
-        $xslfile = C4::Context->preference('marcflavour') . "slim2OPACMARCdetail.xsl";
+        $xslfile = 'plainMARC.xsl';
     }
     $xslfilename = "$htdocs/$theme/$lang/xslt/$xslfile";
     $xslfilename = "$htdocs/$theme/en/xslt/$xslfile" unless ( $lang ne 'en' && -f $xslfilename );