LU-5151 lnet: return +ve for blocked lnet messsage

LU-5151 lnet: return +ve for blocked lnet messsage

returned value of lnet_post_send_locked and
lnet_post_routed_recv_locked are changed to -ve by:
http://review.whamcloud.com/#/c/9369/

this is wrong because callers rely on +ve to identify blocked
message which is not a failure.

To respect linux kernel coding style and not use positive error
code, this patch adds two macros as non-error returned values of
these functions:
  LNET_CREDIT_OK	has credit for message
  LNET_CREDIT_WAIT	no credit and message is blocked

both these functions will return these two values instead of 0
and EAGAIN

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: Id809e4fa6e22780a0bd9ad9c0f0ef96b2c9aa879
Reviewed-on: http://review.whamcloud.com/10625
Tested-by: Jenkins
Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>