Disable backupninja client log output color by default

Related: PROD-28528
Fixes: PROD-32166

Change-Id: I6cdda7705e9e340f3fe60fafe7c440cf3fba0ffe
diff --git a/defaults/backupninja.yml b/defaults/backupninja.yml
index f827173..71e00bf 100644
--- a/defaults/backupninja.yml
+++ b/defaults/backupninja.yml
@@ -3,3 +3,4 @@
     backupninja_engine: rsync
     backupninja_backup_host: 127.0.0.1
     backupninja_public_key: no-key-provided
+    backupninja_color_log: false