e2fsck: update global free blocks/inodes count when truncating orphan inodes

e2fsck: update global free blocks/inodes count when truncating orphan inodes

By the time we start processing the orphan inode list, we have already
calculated the total expected number of free blocks and inodes in
ctx->free_{blocks,inodes}.  This is used to set the free blocks/inodes
count in the superblock in the case where we don't need to do a full
e2fsck.

We need to update these expected free block counts as we process the
orphan inode list so that superblock values are set correctly.
Otherwise we could have the following happen:

% e2fsck /tmp/test.img
e2fsck 1.42.3 (14-May-2012)
Truncating orphaned inode 12 (uid=0, gid=0, mode=0100644, size=0)
Setting free blocks count to 46 (was 79)
/tmp/test.img: clean, 12/16 files, 54/100 blocks

% e2fsck /tmp/test.img
e2fsck 1.42.3 (14-May-2012)
Setting free blocks count to 79 (was 46)
/tmp/test.img: clean, 12/16 files, 21/100 blocks

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