[db,tool,conf] fix thinko in db update suppression

The ``db.update-live`` option caused all db updates, even forced ones to
fail due to a missing check for the kind of run.
fontloader: sync with Context as of 2014-07-29

Closes https://github.com/lualatex/luaotfload/issues/237
Merge pull request #241 from phi-gamma/master

fix issue #237