[PATCH] JFS: Simplify creation of new iag

JFS was creating a new IAG (inode aggregate group) in one address
space, and afterwards, accessing it from another.  This could lead to
complications when cache pages contain more than one page of jfs
metadata.  This patch causes the IAG to be initialized in the same
address space that it is subsequently accessed with.

This also elimitates an I/O, but IAG's aren't created too often.

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>