Fix crash when closing sessions with vendor-specific user types

[akaloti]

Fix #230

In the current version of this package, when using a custom user such as the Crypto User -- represented by value 0x80000001 -- on Thales Luna HSM 7, we run into problems when closing a session because:

• The Session.close() method calls Session.user_type(). (Both methods are defined in pkcs11/_pkcs11.pyx.)
• Session.user_type() then calls UserType().
• UserType(), defined in pkcs11/constants.py, crashes because the custom user value 0x80000001 does not match NOBODY (999), SO (0), or USER (1).

This PR fixes the problem by avoiding the indirect call to UserType() in Session.close(). It also updates Session.user_type() to not crash if the user type is a custom user.

[MatthiasValvekens]

Those failing tests seem to be related to an upstream change (#233). I pushed a change to master to disable the offending test when running against opencryptoki for now.

[akaloti]

Thanks. I merged the change from master into this branch.

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Codecov Report

❌ Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.40%. Comparing base (1ff2114) to head (5367918).
⚠️ Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
pkcs11/_pkcs11.pyx	20.00%	4 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #231      +/-   ##
==========================================
+ Coverage   90.17%   91.40%   +1.23%     
==========================================
  Files          15       15              
  Lines        2625     2677      +52     
  Branches       29       27       -2     
==========================================
+ Hits         2367     2447      +80     
+ Misses        255      228      -27     
+ Partials        3        2       -1     

Flag	Coverage Δ
unittests	91.40% <20.00%> (+1.23%)	⬆️

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[MatthiasValvekens]

Nice work. Thanks!