e2fsck: Fix e2fsck automatic blocksize detetion

e2fsck: Fix e2fsck automatic blocksize detetion

This fixes a regression that was introduced in commit dcc91e10 (it
showed up first in e2fsprogs 1.40.7).  Since we weren't freeing the
filesystem handle, ext2fs_open2() was returning EBUSY, and so this
caused a failure in the code that would automatically determine the
filesystem block size when only the superblock number was specified by
the user.

This was discussed in http://ubuntuforums.org/showthread.php?t=789323,
and Matthias Bannach pointed this out to me, for which I am very
grateful.

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