fixed _TLSSignature show2

[jiuyuan-light]

I found that there is an issue with the show and show2 of _TLSSignature when using it. The expected sig_val for show2 should be "sha384+eccsa".

from scapy.all import raw
sig = _TLSSignature(sig_alg="sha384+ecdsa", sig_val=b"abcd")
sig.show()
sig.show2()
print(raw(sig).hex(), hex(sig.sig_alg))

###[ TLS Digital Signature ]###
  sig_alg   = sha384+ecdsa
  sig_len   = None
  sig_val   = b'abcd'

###[ TLS Digital Signature ]###
  sig_alg   = sha256+rsaepss
  sig_len   = 4
  sig_val   = b'abcd'

0503000461626364 0x503

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.78%. Comparing base (8e7e73b) to head (24d700c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4878      +/-   ##
==========================================
+ Coverage   80.29%   80.78%   +0.48%     
==========================================
  Files         350      368      +18     
  Lines       89937    90262     +325     
==========================================
+ Hits        72215    72916     +701     
+ Misses      17722    17346     -376     

Files with missing lines	Coverage Δ
scapy/layers/tls/keyexchange.py	86.99% <100.00%> (+0.02%)	⬆️

... and 285 files with indirect coverage changes

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