Correct when the the current network global var is set

[xinaxu]

The Action for the flag is only executed when the flag is set.
In go-address package, address.CurrentNetwork is initialized to address.Testnet. So we need to check --lotus-test and set it to address.Mainet if the flag is not set.

[codecov-commenter]

Codecov Report

Merging #167 (5e9c3c1) into main (7230d07) will increase coverage by 0.67%.
Report is 2 commits behind head on main.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #167      +/-   ##
==========================================
+ Coverage   30.82%   31.49%   +0.67%     
==========================================
  Files           5        5              
  Lines         743      743              
==========================================
+ Hits          229      234       +5     
+ Misses        479      474       -5     
  Partials       35       35              

see 1 file with indirect coverage changes