fix core dump issue when disabling HAVE_IBV_WR_API

[tianx666]

When using rdma-core-v44, and compile perftest with "bash autoconfig; configure --disable-ibv_wr_api; make", then run a test. A core dump will ocur while ctx->dci_stream_id[i] is not allocted but assigned 0.

[sshaulnv]

Hi @tianx666, thanks for your contribution!

This change will not fully resolve the issue, as there are additional instances where dci_stream_id is accessed and also HAVE_IBV_WR_API is not directly related to it.
Since this variable is specific to the DC connection type, a more appropriate approach would be to add a check for the selected connection type before accessing it.

[tianx666]

Hi，@sshaulnv
As for accessing dci_stream_id, all other instances are inside new_post_send, which is controlled by HAVE_IBV_WR_API, so there should be no issues.
The code here is just to initialize dci_stream_id to 0 in ctx_init, so it would be better to initialize it directly after allocation.