Fix RAW-OPEN against Samba3

This test assumed that fnums are recycled immediately after a close. This is
not true on Samba 3.

Andrew B., I assume this is just a bug in the test. Assuming recycled fnums
might be true on Windows and Samba 4, but I don't think we should assume this
everywhere.

Volker
(This used to be commit a4c3a59d47b2b1c794eda556d252c61907be1b3c)