RDMA/rtrs-srv: Duplicated session name is not allowed

RDMA/rtrs-srv: Duplicated session name is not allowed

If two clients try to use the same session name, rtrs-server generates a
kernel error that it failed to create the sysfs because the filename
is duplicated.

This patch adds code to check if there already exists the same session
name with the different UUID. If a client tries to add more session,
it sends the UUID and the session name. Therefore it is ok if there is
already same session name with the same UUID. The rtrs-server must fail
only-if there is the same session name with the different UUID.

Link: https://lore.kernel.org/r/20210528113018.52290-17-jinpu.wang@ionos.com
Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Aleksei Marov <aleksei.marov@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>