[djl-serving] Update auto scale algorithm

[frankfliu]

Change-Id: Ib7b8d1dd4f2df95e928967f417dc872040e7e81e

Description

Brief description of what this PR is about

• If this change is a backward incompatible change, why must this change be made?
• Interesting edge cases to note here

[codecov-commenter]

Codecov Report

Merging #1149 (db7481a) into master (eea8c6c) will increase coverage by 0.04%.
The diff coverage is 52.38%.

@@             Coverage Diff              @@
##             master    #1149      +/-   ##
============================================
+ Coverage     70.11%   70.15%   +0.04%     
- Complexity     5323     5326       +3     
============================================
  Files           513      513              
  Lines         23689    23689              
  Branches       2553     2554       +1     
============================================
+ Hits          16610    16620      +10     
+ Misses         5711     5699      -12     
- Partials       1368     1370       +2     

Impacted Files	Coverage Δ
.../main/java/ai/djl/serving/wlm/WorkLoadManager.java	70.70% <47.05%> (+6.62%)	⬆️
...ava/ai/djl/serving/http/DescribeModelResponse.java	90.74% <66.66%> (-1.42%)	⬇️
...src/main/java/ai/djl/serving/wlm/ModelManager.java	80.18% <100.00%> (+0.18%)	⬆️
api/src/main/java/ai/djl/inference/Predictor.java	90.38% <0.00%> (+2.88%)	⬆️

---

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 eea8c6c...db7481a. Read the comment docs.