fix: update token cache considering the cert expiry

[sibicramesh]

// We cache the token only If we are atleast 20 seconds (SynTokenCacheValiditity + 10s)
// away from expiration. This fixes the corner case when the cert is expired and
// we still use the token we cached earlier.

[codecov[bot]]

Codecov Report

Merging #961 into master will decrease coverage by 0.15%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #961      +/-   ##
==========================================
- Coverage   54.46%   54.31%   -0.16%     
==========================================
  Files         122      122              
  Lines       11724    11724              
==========================================
- Hits         6386     6368      -18     
- Misses       4710     4733      +23     
+ Partials      628      623       -5

Impacted Files	Coverage Δ
monitor/extractors/linux.go	48.78% <0%> (-21.96%)	:arrow_down:

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[sibicramesh]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

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