Remove unnecessary check

[gpotter2]

• fixes Failure to set promiscuous mode on interface after #4497 #4525

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.58%. Comparing base (a51bcd5) to head (0132ed0).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4528      +/-   ##
==========================================
+ Coverage   81.36%   81.58%   +0.22%     
==========================================
  Files         356      356              
  Lines       85277    85277              
==========================================
+ Hits        69387    69575     +188     
+ Misses      15890    15702     -188     

Files with missing lines	Coverage Δ
scapy/arch/linux/__init__.py	82.88% <ø> (+0.24%)	⬆️

... and 18 files with indirect coverage changes

[polybassa]

Do you think it makes sense to have a quick test like

set interface down
conf.ifaces.reload()
set interface up
sniff(...)

[gpotter2]

It's probably alright.