mke2fs: throttle progress updates to once a second

mke2fs: throttle progress updates to once a second

With lazy itable initialization, the progress updates for writing the
inode table happens so quickly that on a serial console, the time to
write the progress updates can be the bottleneck.  Fix this by only
updating the progress indicator once a second.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>