properly update reclass_source_path variable

Change-Id: I72ddcf413426861864044861765c06356203a405
diff --git a/bootstrap.sh b/bootstrap.sh
index aa2f5a8..0667f9e 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -251,7 +251,11 @@
   fi
 
   # to force alternative reclass module path
-  RECLASS_SOURCE_PATH=${RECLASS_SOURCE_PATH:-""}
+  if [ -n "$RECLASS_SOURCE_PATH" ]; then
+    RECLASS_SOURCE_PATH="reclass_source_path: ${RECLASS_SOURCE_PATH}"
+  else
+    RECLASS_SOURCE_PATH=""
+  fi
 
   [ ! -d /etc/salt/master.d ] && mkdir -p /etc/salt/master.d
   cat <<-EOF > /etc/salt/master.d/master.conf