Use TEST_GROUP instead of SHORT_TEST_GROUP

Change-Id: I7b76112c418acf7c5dacd7492dacd3e9b7d7cd5b
diff --git a/src/com/mirantis/mk/Test.groovy b/src/com/mirantis/mk/Test.groovy
index d28dfaa..b8ae78c 100644
--- a/src/com/mirantis/mk/Test.groovy
+++ b/src/com/mirantis/mk/Test.groovy
@@ -126,7 +126,7 @@
                            "-e TESTRAIL_PLAN_NAME=${plan} " +
                            "-e TESTRAIL_MILESTONE=${milestone} " +
                            "-e TESTRAIL_SUITE=${suite} " +
-                           "-e SHORT_TEST_GROUP=${testGroup} " +
+                           "-e TEST_GROUP=${testGroup} " +
                            "${image}"
     if (master == null) {
       sh("${command}")