[dbnode] Add logs for the effective query index concurrency and max worker time at startup

[robskillington]

What this PR does / why we need it:

Adds some minor logs on the effective query index concurrency and index max worker time.

Special notes for your reviewer:

Does this PR introduce a user-facing and/or backwards incompatible change?:

NONE

Does this PR require updating code package or user-facing documentation?:

NONE

[codecov]

Codecov Report

Merging #3642 (eb72a77) into master (eb72a77) will not change coverage.
The diff coverage is n/a.

❗ Current head eb72a77 differs from pull request most recent head dec2d74. Consider uploading reports for the commit dec2d74 to get more accurate results

@@          Coverage Diff           @@
##           master   #3642   +/-   ##
======================================
  Coverage    56.4%   56.4%           
======================================
  Files         551     551           
  Lines       61868   61868           
======================================
  Hits        34900   34900           
  Misses      23856   23856           
  Partials     3112    3112           

Flag	Coverage Δ
aggregator	57.1% <0.0%> (ø)
cluster	∅ <0.0%> (∅)
collector	58.4% <0.0%> (ø)
dbnode	61.0% <0.0%> (ø)
m3em	46.4% <0.0%> (ø)
metrics	19.8% <0.0%> (ø)
msg	74.4% <0.0%> (ø)

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