mke2fs: load configfile blocksize setting before 64bit checks

mke2fs: load configfile blocksize setting before 64bit checks

mke2fs has a series of checks to ensure that we don't create a
filesystem too big for its blocksize -- if auto-64bit is on, then it
turns on 64bit; otherwise it complains.  Unfortunately, it performs
these checks before looking in mke2fs.conf for a blocksize, which
means that the checks are incorrect if the user specifies a non-4096
blocksize in the config file and says nothing on the command line.
The bug also has the effect of mandating a 4k block size on any block
device larger than 4T in that situation.  Therefore, read the block
size from the config file before performing the 64bit checks.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>