vfs_prealloc: Remove call to gpfs_prealloc

vfs_prealloc: Remove call to gpfs_prealloc

Calling gpfs_prealloc changes the actual size of the file, and this
should not be done implicitly. Also this code does not compile due to
the missing dependency to the gpfs library. The best way solution here
is probably removing the call to gpfs_prealloc. The vfs_gpfs module
already implements the call to gpfs_prelloc when this can be done
safely.

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Feb 11 02:03:09 CET 2015 on sn-devel-104