Tweak to make trait conversion (e.g. LMA->SLA) less random

Per discussion at gh-245, setting the random seed before doig trait conversion
should prevent re-run of meta-analysis when forceupdate=AUTO (if traits really
haven't changed since last run).
Merge pull request #252 from ryankelly-uiuc/fix_query.trait.data

Tweak to make trait conversion (e.g. LMA->SLA) less random