mf.resolvable: reduce timeout by one second (so < plugin.timeout)

[msimerson]

fixes #2448

Changes proposed in this pull request:

• reduce default timeout by one second (so < plugin.timeout)
• reduce timeout if its >= plugin.timeout

[codecov]

Codecov Report

Merging #2544 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2544   +/-   ##
=======================================
  Coverage   59.45%   59.45%           
=======================================
  Files          28       28           
  Lines        6200     6200           
  Branches     1543     1543           
=======================================
  Hits         3686     3686           
  Misses       2514     2514

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