LU-13053 tests: fix conf-sanity call to umount_ldiskfs

LU-13053 tests: fix conf-sanity call to  umount_ldiskfs

conf-sanity test 87 calls umount_ldiskfs(), but the function
in test-framework.sh is unmount_ldiskfs().  We need to
change the function call in test 87 to unmount_ldiskfs().

Test-Parameters: trivial testlist=conf-sanity
Signed-off-by: James Nunez <jnunez@whamcloud.com>
Change-Id: I3e0818a229341c4fab8aee923cad2253b7dd634d
Reviewed-on: https://review.whamcloud.com/36949
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>