rdma: Add batch command support

rdma: Add batch command support

Implement an option (-b) to execute RDMAtool commands
from supplied file. This follows the same model as
in use for ip and devlink tools, by expecting
every new command to be on new line.

These commands are expected to be without any -*
(e.g. -d, -j, e.t.c) global flags, which should be
called externally.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>