user: speed up user stats computation

It can take a while to fetch the data from FlightStats (about 500ms per query).
This patch parallelizes the queries. In practice, the view is cached though.

Signed-off-by: diditclear <didyourupgradeclear@gmail.com>
logger: improve logging

Signed-off-by: diditclear <didyourupgradeclear@gmail.com>