Use @wraps decorator

Use @wraps decorator from the functools library.
This calls the update_wrapper method from functools
which sets these built-in values to those of the wrapped function.

Change-Id: Ie5a6cd71db5cc645c7fc7d1a5bcad5f0bcf651fd
diff --git a/tempest/lib/decorators.py b/tempest/lib/decorators.py
index e78e624..6ed99b4 100644
--- a/tempest/lib/decorators.py
+++ b/tempest/lib/decorators.py
@@ -69,12 +69,11 @@
                                "or False") % attr
 
     def __call__(self, func):
+        @functools.wraps(func)
         def _skipper(*args, **kw):
             """Wrapped skipper function."""
             testobj = args[0]
             if not getattr(testobj, self.attr, False):
                 raise testtools.TestCase.skipException(self.message)
             func(*args, **kw)
-        _skipper.__name__ = func.__name__
-        _skipper.__doc__ = func.__doc__
         return _skipper