Fix service start in salt-models testing

Change-Id: I500481324da315594b3321070a229a27f3f7e50e
diff --git a/src/com/mirantis/mk/SaltModelTesting.groovy b/src/com/mirantis/mk/SaltModelTesting.groovy
index e0adcad..6f67da1 100644
--- a/src/com/mirantis/mk/SaltModelTesting.groovy
+++ b/src/com/mirantis/mk/SaltModelTesting.groovy
@@ -85,7 +85,7 @@
 
         branches["DEBUG"] = {
           while (!jobFinished) {
-            sh("service salt-master start && sleep 30")
+            sh("(service salt-master start || true) && sleep 30")
           }
         }