Fixed broken path joins and unclosed files

[DPeled]

Description

After a bug occurred to me while running over Windows, I found out that there are a lot places in the code where there is a path join using string concatenation and not with os.path.join which creates some broken paths and results some errors while serving models. In my ways of changing it, I've noticed that there are some bugs of unclosed file descriptors that were just left open, so I clodes them too.

Fixes #1708, fixes #1686

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Feature/Issue validation/testing

Checklist:

• Did you have fun?
• Have you added tests that prove your fix is effective or that this feature works?
• Has code been commented, particularly in hard-to-understand areas?
• Have you made corresponding changes to the documentation?

[msaroufim]

Very cool thank you for improving the Torchserve user experience on Windows. I still see a few stragglers left. Might as well fix those as well and we should be able to easily merge this

[msaroufim]

Hi @DPeled are you still interested in finishing this PR? Just a few minor comments left and we can merge

[DPeled]

@msaroufim I'll work on it soon, I didn't have much time at the last weeks

[DPeled]

@msaroufim @lxning I've read your review and I replied as well.
Please take a look hopefully you'll understand my answers and why I answered it.

[mreso]

LGTM
@msaroufim Should we suggest usage of pathlib instead of os.path for future developments?

[msaroufim]

Probably a good boot camp task template we can setup @mreso

[agunapal]

Looks good

[DPeled]

@msaroufim Hi is there something to do with the tasks that failed?
From the logs I can see that because some packages not installed or torchserver.exe was not recognized in windows.
It doesn't seems to fail as a result from my PR

[msaroufim]

I kicked off CI again let's see what happens

[codecov]

Codecov Report

Merging #1709 (49cc745) into master (aa2468d) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1709   +/-   ##
=======================================
  Coverage   45.28%   45.28%           
=======================================
  Files          64       64           
  Lines        2597     2597           
  Branches       60       60           
=======================================
  Hits         1176     1176           
  Misses       1421     1421           

Impacted Files	Coverage Δ
ts/model_server.py	0.00% <ø> (ø)
ts/model_loader.py	81.17% <100.00%> (ø)

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[msaroufim]

@DPeled can you please fix the lint error with pre-commit instructions are the bottom of the failed action. Also the GPU check needs to pass