Making CONTINUE_IF_NO_PROXY attribute configurable

[namrathaurs]

Addresses #442 (linked to this PR; see under Development section).

[codecov[bot]]

Codecov Report

Patch coverage: 20.00% and project coverage change: -0.14 :warning:

Comparison is base (07292a4) 47.36% compared to head (dc0250d) 47.23%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #457 +/- ## ========================================== - Coverage 47.36% 47.23% -0.14% ========================================== Files 54 54 Lines 2903 2907 +4 Branches 497 498 +1 ========================================== - Hits 1375 1373 -2 - Misses 1427 1433 +6 Partials 101 101 ``` | Flag | Coverage Δ | | |---|---|---| | python-3.8 | `47.23% <20.00%> (-0.10%)` | :arrow_down: | | python-3.9 | `47.23% <20.00%> (-0.14%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=HEPCloud#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://app.codecov.io/gh/HEPCloud/decisionengine_modules/pull/457?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=HEPCloud) | Coverage Δ | | |---|---|---| | [...engine\_modules/glideinwms/glideinwms\_config\_lib.py](https://app.codecov.io/gh/HEPCloud/decisionengine_modules/pull/457?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=HEPCloud#diff-c3JjL2RlY2lzaW9uZW5naW5lX21vZHVsZXMvZ2xpZGVpbndtcy9nbGlkZWlud21zX2NvbmZpZ19saWIucHk=) | `19.04% <ø> (ø)` | | | [...ngine\_modules/glideinwms/glide\_frontend\_element.py](https://app.codecov.io/gh/HEPCloud/decisionengine_modules/pull/457?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=HEPCloud#diff-c3JjL2RlY2lzaW9uZW5naW5lX21vZHVsZXMvZ2xpZGVpbndtcy9nbGlkZV9mcm9udGVuZF9lbGVtZW50LnB5) | `10.97% <20.00%> (-0.25%)` | :arrow_down: |

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[mambelli]

I changed CONTINUE_IF_NO_PROXY to True by default since tokens are the most common config in DE 2.x