log.debug()/info()/warn()/error() must not fail on formatting errors

[rtsisyk]

tarantool> log.info('%d', nil)

---
- error: 'builtin/log.lua:26: bad argument #2 to ''format'' (number expected, got
    nil)'
...

The application should not crash due to logging problems!
Log functions must print something reasonable instead of failing on string.format().
Please add extra pcall there.

[kostja]

• Roman Tsisyk notifications@github.com [15/07/01 16:18]:

I did something similar for format() of strings AFAIR.

http://tarantool.org - a NoSQL database in a Lua script

[kostja]

This goes to the master branch.