RDMA/core: Fixes for port mapper client registration

Fixes to allow clients to make remove mapping requests, after
they have provided the user space service with the mapping
information, they are using when the service is restarted.

1) Adding IWPM_REG_VALID, IWPM_REG_INCOMPL and IWPM_REG_UNDEF
   registration types for the port mapper clients and functions
   to set/check the registration type.
2) If the port mapper user space service is not available to register
   the client, then its registration stays IWPM_REG_UNDEF and the
   registration isn't checked until the service becomes available
   (no mappings are possible, if the user space service isn't running).
3) After the service is restarted, the user space port mapper pid is set
   to valid and the client registration is set to IWPM_REG_INCOMPL
   to allow the client to make remove mapping requests.

Signed-off-by: Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>