ocfs2: Handle quota file corruption more gracefully

ocfs2_read_virt_blocks() does BUG when we try to read a block from a file
beyond its end. Since this can happen due to filesystem corruption, it
is not really an appropriate answer. Make ocfs2_read_quota_block() check
the condition and handle it by calling ocfs2_error() and returning EIO.

[ Modified to print ip_blkno in the error - Joel ]

Reported-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>