Fix typo for SetupDockerAndTest function

Change-Id: If55bbb2ee7a59d5e88f3c728ae6619705c9d16a6
diff --git a/src/com/mirantis/mk/SaltModelTesting.groovy b/src/com/mirantis/mk/SaltModelTesting.groovy
index 0016d70..3e551f6 100644
--- a/src/com/mirantis/mk/SaltModelTesting.groovy
+++ b/src/com/mirantis/mk/SaltModelTesting.groovy
@@ -92,7 +92,7 @@
 """
         def extraRepoMergeStrategy = config.get('extraRepoMergeStrategy', 'merge')
         def extraReposYaml = null
-        if (defaultMergeStrategy == 'merge') {
+        if (extraRepoMergeStrategy == 'merge') {
             def extraReposYamlConfig = config.get('extraReposYaml', '')
             def extraRepos = readYaml text: extraReposYamlConfig
             def defaultRepos = readYaml text: defaultExtraReposYaml