python: fix bindings that don't raise an exception

For example:
 >>> dom.memoryStats()
 libvir: QEMU Driver error : Requested operation is not valid:\
         domain is not running

There are six such python API functions like so.
The root reason is that generator.py script checks the type of return
value of a python stub function defined in libvirt-api.xml or
libvirt-override-api.xml to see whether to add the raise clause or not
in python wrapper code in libvirt.py.

The type of return value is supposed to be C types.
For those stub functions which return python non-integer data type like
string, list, tuple, dictionary, the existing type in functions varies
from each other which leads problem like this.

Currently, in generator.py, it maintains a buggy whitelist for stub functions
returning a list type. I think it is easy to forget adding new function name
in the whitelist.

This patch makes the value of type consistent with C type "char *"
in libvirt-override-api.xml. For python, any of types could be printed
as string, so I choose "char *" in this case. And the comment in xml
could explain it when adding new function definition.

      <function name='virNodeGetCPUStats' file='python'>
        ...
 -      <return type='virNodeCPUStats' info='...'/>
 +      <return type='char *' info='...'/>
        ...
      </function>

generator.py

@@ -1009,11 +1009,9 @@ functions_list_exception_test = {
 }
 functions_list_default_test = "%s is None"
 
-def is_list_type (name):
-    whitelist = [ "virDomainBlockStats",
-                  "virDomainInterfaceStats" ]
+def is_python_noninteger_type (name):
 
-    return name[-1:] == "*" or name in whitelist
+    return name[-1:] == "*"
 
 def nameFixup(name, classe, type, file):
     # avoid a desastrous clash
@@ -1387,7 +1385,7 @@ def buildWrappers(module):
                                        ("ret", name))
                     classes.write("    return ret\n")
 
-                elif is_list_type (ret[0]):
+                elif is_python_noninteger_type (ret[0]):
                     if not functions_noexcept.has_key (name):
                         if functions_list_exception_test.has_key (name):
                             test = functions_list_exception_test[name]
@@ -1657,7 +1655,7 @@ def buildWrappers(module):
 
                         classes.write ("        return ret\n")
 
-                    elif is_list_type (ret[0]):
+                    elif is_python_noninteger_type (ret[0]):
                         if not functions_noexcept.has_key (name):
                             if functions_list_exception_test.has_key (name):
                                 test = functions_list_exception_test[name]