[SSLv2] s/debug_dissect/debug_dissector/

[evverx]

to prevent do_dissect_payload from failing with

  File "scapy/scapy/layers/tls/record_sslv2.py", line 177, in do_dissect_payload
    if conf.debug_dissect:
       ^^^^^^^^^^^^^^^^^^
  File "scapy/scapy/config.py", line 950, in __getattribute__
    return object.__getattribute__(self, attr)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Conf' object has no attribute 'debug_dissect'

The test is added to exercise the Exception clause.

(I accidentally spotted it in #4082 (comment) but forgot to send a PR)

[codecov]

Codecov Report

Merging #4129 (57c5fa5) into master (219f2fe) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4129   +/-   ##
=======================================
  Coverage   80.95%   80.96%           
=======================================
  Files         330      330           
  Lines       76234    76234           
=======================================
+ Hits        61714    61721    +7     
+ Misses      14520    14513    -7     

Files Changed	Coverage Δ
scapy/layers/tls/record_sslv2.py	90.50% <100.00%> (+4.46%)	⬆️

... and 3 files with indirect coverage changes