resize2fs: fix regression test to not depend on ext4.ko being loaded

resize2fs: fix regression test to not depend on ext4.ko being loaded

The behavior of the r_fixup_lastbg_big test varies depending on
whether or not ext4.ko is loaded and supports lazy_itable_init.  This
makes checking the bg flags after resize2fs hard to predict, so put in
a way to force resize2fs to zero the inode tables, and compare the
output based on lazy_itable_init == 0.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>