salt: Prevent invalid escape sequence warnings

We need to pass `\;` to the `isoinfo` binary for reading file contents
from an ISO archive, but this escape sequence is not valid in Python,
and Python 3 warns about it.
We could have escaped the backslash, but instead rely on the raw string
notation for Python 3 (`r'my \escaped sequence'`).

salt/_modules/metalk8s.py

@@ -171,7 +171,7 @@ def archive_info_from_iso(path):
 
     cmd = ' '.join([
         'isoinfo',
-        '-x', '/PRODUCT.TXT\;1',
+        '-x', r'/PRODUCT.TXT\;1',
         '-i', '"{}"'.format(path),
     ])
     result = __salt__['cmd.run_all'](cmd=cmd)

salt/_modules/metalk8s_solutions.py

@@ -302,7 +302,7 @@ def manifest_from_iso(path):
 
     cmd = ' '.join([
         'isoinfo',
-        '-x', '/{}\;1'.format(SOLUTION_MANIFEST.upper()),
+        '-x', r'/{}\;1'.format(SOLUTION_MANIFEST.upper()),
         '-i', '"{}"'.format(path),
     ])
     result = __salt__['cmd.run_all'](cmd=cmd)