rpc: Work around epydoc warning
rpc: Work around epydoc warning

Aliasing the “threading” module allows us to avoid the “No information
available for ganeti.rpc._RpcThreadLocal's base threading.local” warning
by epydoc.

Signed-off-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Reviewed-by: René Nussbaumer <bc755ac45a0e799d1d490cba76febc56d80cc5fc@google.com>

ganeti-github-testing/ganeti-test-1,mbakke/ganeti,andir/ganeti,leshchevds/ganeti,dimara/ganeti,yiannist/ganeti,ganeti/ganeti,apyrgio/ganeti,mbakke/ganeti,yiannist/ganeti,apyrgio/snf-ganeti,andir/ganeti,yiannist/ganeti,leshchevds/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,grnet/snf-ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,grnet/snf-ganeti,apyrgio/ganeti,bitemyapp/ganeti,ganeti/ganeti,andir/ganeti,bitemyapp/ganeti,onponomarev/ganeti,leshchevds/ganeti,dimara/ganeti,mbakke/ganeti