import: Make progress reporting a bit less crazy
We do so by flushing the output after printing it, and increasing
the PROGRESS_INTERVAL to 25000 lines (up from 500). This makes
the character marker appear to stand still at the beginning of the
line and also doesn't cause the ETA to jump so wildly all the time.
The interval of 25000 lines is still low enough to make updates
happen several times per second, even in the cold-cache case on
my slow laptop-disks, so it will surely suffice for real-world
use.
Signed-off-by: Andreas Ericsson <ae@op5.se>