LU-9439 scripts: Change behavior of lustre_rmmod

The lustre_rmmod script was modified to take an arbitrary list of
modules and try to remove them and any modules dependent on them.
Previously its behavior was to always remove the libcfs module,
along with either the ldiskfs or another module passed as a
parameter.

The old interface was roughly maintained. Any of the following
commands will remove the ldiskfs, libcfs, and all dependent modules:

    $ lustre_rmmod
    $ lustre_rmmod ldiskfs
    $ lustre_rmmod ldiskfs libcfs

The benefit now, is that any other list of modules can be specified
without removing libcfs. For example, the following command will only
remove ptlrpc and its dependent modules (leaving libcfs intact):

    $ lustre_rmmod ptlrpc

The lnet init script was modified to perform a lustre_rmmod ptlrpc
before performing an lctl network down. By removing the ptlrpc
module, we can ensure that lnet is not in use. This will help
systems running lustre to shut down cleanly.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Change-Id: I3fbb33ccb00eb96c255c702b238af9d46768954b
Reviewed-on: https://review.whamcloud.com/27213
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>