[lldb] Fix output for unconditionally decorated tests

A missing call to `format` resulted in curly braces getting printed in
the reason a test was modified by a decorator. For example it would
print "{} unconditionally" instead of "skipping unconditionally" for
tests that were marked as such.

lldb/packages/Python/lldbsuite/test/decorators.py

@@ -248,7 +248,7 @@ def _decorateTest(mode,
                 reason_str = "{} due to the following parameter(s): {}".format(
                     mode_str, reason_str)
             else:
-                reason_str = "{} unconditionally"
+                reason_str = "{} unconditionally".format(mode_str)
             if bugnumber is not None and not six.callable(bugnumber):
                 reason_str = reason_str + " [" + str(bugnumber) + "]"
         return reason_str