Fix comparing dictionaries for changes detection

Non-unicode and unicode dicts cannot be compared.
That makes paunch failing to detect config changes and
rebuilding containers w/o a need.

Use yaml safe_load in order to produce a non-unicode dict
for the right comparison of config data.

Change-Id: I507f4b07af2c515fd8548af7dbe6b35ad2a269a9
Closes-Bug: #1810690
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>

paunch/builder/base.py

@@ -16,6 +16,7 @@ import json
 import re
 import shutil
 import tenacity
+import yaml
 
 from paunch.utils import common
 from paunch.utils import systemd
@@ -133,7 +134,7 @@ class BaseBuilder(object):
                 continue
 
             try:
-                ex_data = json.loads(str(ex_data_str))
+                ex_data = yaml.safe_load(str(ex_data_str))
             except Exception:
                 ex_data = None