LU-11071 build: use --with-linux-obj for ubuntu

LU-11071 build: use --with-linux-obj for ubuntu

We can use --with-linux-obj instead of --with-linux-config
the config will be found just under LINUX_OBJ.
Otherwise the configure could fail if LINUX and LINUX_OBJ
are different paths. e.g. ubuntu18

Test-Parameters: trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: Ibaa159e5611c4054b3987da0ce3a8bca2992e057
Reviewed-on: https://review.whamcloud.com/33145
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>