Convert time into integers before storing into database

[jpflori]

Fixes for issue #5612

[codecov]

Codecov Report

Merging #5613 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5613   +/-   ##
=======================================
  Coverage   89.95%   89.95%           
=======================================
  Files         352      352           
  Lines       38043    38043           
=======================================
  Hits        34222    34222           
  Misses       3821     3821           

Impacted Files	Coverage Δ
master/buildbot/db/builds.py	98.56% <ø> (ø)
master/buildbot/db/sourcestamps.py	98.92% <ø> (ø)
master/buildbot/db/steps.py	99.05% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 38dbae5...b533030. Read the comment docs.

[tardyp]

thanks!