ext2fs: avoid re-reading inode multiple times

ext2fs: avoid re-reading inode multiple times

Reduce the number of times that the inode is read from storage.
Factor ext2fs_xattrs_read() into a new ext2fs_xattrs_read_inode()
function that can accept an in-memory inode, and call that from
within ext2fs_xattrs_read() and in e2fsck_pass1() when the inode
is already available.

Similarly, in e2fsck_pass4() avoid re-reading the inode multiple
times in disconnect_inode(), check_ea_inode(), and in the main
function body if possible.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>