Add PoE config for Juniper devices

[stveit]

Fixes #2633

Adds backend for getting current state for juniper interfaces and changing the state

I will add more /better tests

also the code smells will be fixed..

[codecov]

Codecov Report

Merging #2666 (e9cf952) into master (e879e67) will decrease coverage by 0.05%.
Report is 4 commits behind head on master.
The diff coverage is 27.27%.

@@            Coverage Diff             @@
##           master    #2666      +/-   ##
==========================================
- Coverage   55.19%   55.14%   -0.05%     
==========================================
  Files         561      561              
  Lines       40917    40983      +66     
==========================================
+ Hits        22584    22602      +18     
- Misses      18333    18381      +48     

Files	Coverage Δ
python/nav/portadmin/handlers.py	46.49% <100.00%> (+1.44%)	⬆️
python/nav/portadmin/napalm/juniper.py	40.95% <23.80%> (-4.94%)	⬇️

... and 1 file with indirect coverage changes

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[github-actions]

Test results

     12 files       12 suites   13m 10s ⏱️
3 239 tests 3 239 ✔️ 0 💤 0 ❌
9 192 runs  9 192 ✔️ 0 💤 0 ❌

Results for commit 9659a76.

♻️ This comment has been updated with latest results.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

No Coverage information
0.0% Duplication

[lunkwill42]

Don't really have much to pick on here, except for the obvious duplicates of #2635 (moving around of test fixtures, and adding new exception classes)

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[lunkwill42]

Looks OK to me. Looking forward to testing against actual equipment :)