scm, ucm: add pkey, pkey_index, sl override for QP's

scm, ucm: add pkey, pkey_index, sl override for QP's

On a per open basis, add environment variables
DAPL_IB_SL and DAPL_IB_PKEY and use on
connection setup (QP modify) to override default
values of 0 for SL and PKEY index. If pkey is
provided then find the pkey index with
ibv_query_pkey for dev_attr.max_pkeys.
Will be used for RC and UD type QP's.

Signed-off-by: Arlin Davis <arlin.r.davis@intel.com>