Fix race in Naming_Tools.Register when contexts are created concurrently

[gdepacetest]

Problem

PolyORB.CORBA_P.Naming_Tools.Register fails when two processes register names under the same, not yet existing, naming context at the same time. For example, two servers register DogPark/North and DogPark/South against one po_cos_naming.

1. Both servers call Retrieve_Context, both get NotFound from resolve, and both call bind_new_context for DogPark.
2. The second bind_new_context raises AlreadyBound. Retrieve_Context doesn't handle it, so it propagates into Register.
3. Register has an AlreadyBound handler around the whole procedure, meant for its own bind. It catches this exception while Context is still nil:
   • with Rebind => True, it calls rebind on the nil context and raises CORBA.INV_OBJREF;
   • with Rebind => False, it re-raises AlreadyBound for a name that was never bound.

How to reproduce

Start po_cos_naming, then start two servers at the same moment that each call:

PolyORB.CORBA_P.Naming_Tools.Register ("Parks/<unique name>", Ref, Rebind => True);

In our test (two PolyORB servers on one machine, started together), one of them failed with CORBA.INV_OBJREF from CosNaming.NamingContext.Rebind in about 7 of 10 runs:

raised CORBA.INV_OBJREF : 00000000N
Corba.Raise_Inv_Objref at corba.adb:411
Cosnaming.Namingcontext.Rebind at cosnaming-namingcontext.adb:273
Polyorb.Corba_P.Naming_Tools.Register at polyorb-corba_p-naming_tools.adb:185

Fix

• Retrieve_Context: if bind_new_context raises AlreadyBound, another client created the context in the meantime, so resolve it again and use that context.
• Register: the AlreadyBound handler now covers only bind (Context, N, Ref), so it only runs when the name itself is already bound.

Testing

• PolyORB builds with its usual flags (-gnaty -gnatwae).
• Our two-server scenario ran 20 times with no registration failure, compared with about 7 failures in 10 runs before the fix.

[CLAassistant]

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