OpenBSD: fix tests and disallow LibreSSL

[gpotter2]

This:

• disables cryptography usage when LibreSSL is detected. See On some plateforms, DHParameterNumbers performance is 100x slower pyca/cryptography#14048. See the link alex posted, in some cases it's up to 50.000 times slower. It seems to be a wontfix from the mail thread, so we're just disabling it.
• fixes other tests on OpenBSD

[codecov]

Codecov Report

❌ Patch coverage is 44.00000% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.84%. Comparing base (9c3d51c) to head (7743074).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/config.py	50.00%	6 Missing ⚠️
scapy/contrib/automotive/autosar/secoc.py	0.00%	1 Missing ⚠️
scapy/contrib/macsec.py	0.00%	1 Missing ⚠️
scapy/contrib/psp.py	0.00%	1 Missing ⚠️
scapy/layers/dot11.py	0.00%	1 Missing ⚠️
scapy/layers/inet.py	75.00%	1 Missing ⚠️
scapy/layers/inet6.py	66.66%	1 Missing ⚠️
scapy/layers/ipsec.py	0.00%	1 Missing ⚠️
scapy/layers/tls/__init__.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4888      +/-   ##
==========================================
+ Coverage   80.29%   80.84%   +0.55%     
==========================================
  Files         351      369      +18     
  Lines       90618    90961     +343     
==========================================
+ Hits        72763    73539     +776     
+ Misses      17855    17422     -433     

Files with missing lines	Coverage Δ
scapy/contrib/automotive/autosar/secoc.py	88.00% <0.00%> (+0.24%)	⬆️
scapy/contrib/macsec.py	95.17% <0.00%> (+0.03%)	⬆️
scapy/contrib/psp.py	93.44% <0.00%> (+0.10%)	⬆️
scapy/layers/dot11.py	91.46% <0.00%> (+0.01%)	⬆️
scapy/layers/inet.py	71.90% <75.00%> (+0.07%)	⬆️
scapy/layers/inet6.py	88.53% <66.66%> (-0.04%)	⬇️
scapy/layers/ipsec.py	90.00% <0.00%> (+0.01%)	⬆️
scapy/layers/tls/__init__.py	50.00% <0.00%> (+10.00%)	⬆️
scapy/config.py	79.16% <50.00%> (-0.44%)	⬇️

... and 278 files with indirect coverage changes

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[gpotter2]

/packit build