DAOS-12829 cart: Fix epi ASSERTs when untracking

[liw]

Commit 53d66d7 might have introduced the following "epi != NULL" assertion failure in crt_context_req_untrack.

#0  raise () from /usr/lib64/libc.so.6
#1  abort () from /usr/lib64/libc.so.6
#2  __assert_fail_base.cold.0 () from /usr/lib64/libc.so.6
#3  __assert_fail () from /usr/lib64/libc.so.6
#4  crt_context_req_untrack (rpc_priv=rpc_priv@entry=0x55a254b83150)
    at src/cart/crt_context.c:1358
        crt_ctx = 0x55a25465f500
        epi = 0x0
        submit_list = {next = 0x0, prev = 0x4}
        tmp_rpc = <optimized out>
        rc = <optimized out>
        __func__ = "crt_context_req_untrack"
        __PRETTY_FUNCTION__ = "crt_context_req_untrack"
#5  crt_hg_req_send_cb (hg_cbinfo=<optimized out>) at
    src/cart/crt_hg.c:1287
        rpc_pub = <optimized out>
        rpc_priv = <optimized out>
        hg_ret = HG_SUCCESS
        rc = 0
        __func__ = "crt_hg_req_send_cb"
        __PRETTY_FUNCTION__ = "crt_hg_req_send_cb"
        __rc = <optimized out>

The RPC might be an outgoing URI_LOOKUP request, which we don't track. Hence its crp_epi field was NULL as expected. Commit 53d66d7 should have asserted "epi != NULL" after making sure that the RPC is not an URI_LOOKUP request. This patch does that and removes a few useless lines from crt_context_req_untrack_internal.

Test-tag: pr dynamic_server_pool OSAOfflineExtend NvmePoolExtend

Required-githooks: true

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[github-actions]

Bug-tracker data:
Ticket title is 'ior: rpc EMRG src/cart/crt_context.c:1358 crt_context_req_untrack() Assertion 'epi != NULL' failed'
Status is 'In Progress'
Labels: 'ci_impact,triaged,weekly_test'
https://daosio.atlassian.net/browse/DAOS-12829

[daosbuild1]

LGTM. No errors found by checkpatch.