LU-2068 build: Respect "--without-ldiskfs" option

The "--without-ldiskfs" configure option was not properly
being respected by a few of the Makefiles. This change is
an attempt to remedy this issue. Now, one should be able
to disable building ldiskfs and the related lvfs and osd
code with "--without-ldiskfs".

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Change-Id: I502e125639a60f62a37e3f95ecc943dedc37f5ea
Reviewed-on: http://review.whamcloud.com/4148


Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>