ensure that gz compression test is run with gz

The framework can be configured to use different compression algorithms
to test different ones, but a testcase testing for gz support should
always be run with gz, regardless of what compressions are configured
otherwise.

Git-Dch: Ignore

test/integration/test-compressed-indexes

@@ -5,6 +5,7 @@ TESTDIR=$(readlink -f $(dirname $0))
 . $TESTDIR/framework
 
 setupenvironment
+configcompression '.' 'gz' # only gz is supported for this, so ensure it is used
 configarchitecture "i386"
 
 buildsimplenativepackage "testpkg" "i386" "1.0"