rdma_cm: Detect recursive calls to rdma_seterrno()

rdma_cm: Detect recursive calls to rdma_seterrno()

If rdma_seterrno() is called in a recursive fashion, the
result is that errno ends up set to -1.  Fix the original
occurrence of where this occurs and update rdma_seterrno()
to avoid it modifying errno incorrectly.

Problem reported by hookenz@gmail.com.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>