Set Salt 2017.7 as default Botstrap salt version

Change-Id: I77977c50030f2b63f4c353b919259eea67b3bcf5
diff --git a/bootstrap.sh b/bootstrap.sh
index a4e008b..da78964 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -78,7 +78,7 @@
 # saltstack
 BOOTSTRAP_SALTSTACK=${BOOTSTRAP_SALTSTACK:-True}
 BOOTSTRAP_SALTSTACK_COM=${BOOTSTRAP_SALTSTACK_COM:-"https://bootstrap.saltstack.com"}
-BOOTSTRAP_SALTSTACK_VERSION=${BOOTSTRAP_SALTSTACK_VERSION:- stable 2016.3 }
+BOOTSTRAP_SALTSTACK_VERSION=${BOOTSTRAP_SALTSTACK_VERSION:- stable 2017.7 }
 BOOTSTRAP_SALTSTACK_VERSION=${BOOTSTRAP_SALTSTACK_VERSION//latest*/stable}
 # TODO add 'r' option by default
 # Currently, without 'r' option, upstream saltstack repos will be used. Otherwise