r13583: Realise that the member server name appears in all calls that use the

r13583: Realise that the member server name appears in all calls that use the
credentials.

Consistantly rename these elements in the IDL to computer_name.

Fix the server-side code to always lookup by this name.

Add new, even nastier tests to RPC-SCHANNEL to prove this.

Andrew Bartlett
(This used to be commit 341a0abeb4a9f88d64ffd4681249cb1f643a7a5a)