mke2fs: throttle allocating groups progress as well

mke2fs: throttle allocating groups progress as well

Throttle updates for the "Allocating Groups" progress updates to once
a second as well.  We now do this throttling in libext2fs, so we don't
have to do this for each of mke2fs's progress updates, and because the
updates from ext2fs_allocate_tables() come from within libext2fs
anyway.

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