Fix stacks test

[sdimitro]

Commit:

drgn fixed the bug where runnable threads are distinguished
from running threads and thus it correctly goes to look for
them in memory instead of the PRSTATUS notes.

drgn commit:
github.com/osandov/drgn/commit/eea5422546004d29f85e4d0b94d62fd7564db15a

Side Commit:

Eliminate some dead code for internal __init__.py files

[codecov-commenter]

Codecov Report

Merging #227 into master will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #227      +/-   ##
==========================================
+ Coverage   87.18%   87.29%   +0.11%     
==========================================
  Files          60       60              
  Lines        2465     2456       -9     
==========================================
- Hits         2149     2144       -5     
+ Misses        316      312       -4     

Impacted Files	Coverage Δ
sdb/commands/internal/__init__.py	100.00% <ø> (+20.00%)	⬆️
sdb/commands/linux/internal/__init__.py	100.00% <ø> (+20.00%)	⬆️
sdb/commands/spl/internal/__init__.py	100.00% <ø> (+20.00%)	⬆️
sdb/commands/stacks.py	95.55% <0.00%> (-1.49%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 78f6063...bc14ae1. Read the comment docs.