resource module: wrap traversal operations with clear_err_message ()

Recent debugging revealed that the traverser error message wasn't
getting cleared after some traversal operations, leading to spurious or
error logging that can be unrelated to the error cause.

Wrap each traverser function call with clear_err_message () to ensure
error messages are correctly attributed to the cause.

resource/modules/resource_match.cpp

@@ -1196,6 +1196,7 @@ static int mark_now (std::shared_ptr<resource_ctx_t> &ctx,
     }
     if ((rc = decode_rankset (ctx, ids, ranks)) < 0)
         goto done;
+    ctx->traverser->clear_err_message ();
     if ((rc = ctx->traverser->mark (ranks, status)) < 0) {
         flux_log_error (ctx->h,
                         "%s: traverser::mark: %s",
@@ -1648,6 +1649,7 @@ static int run (std::shared_ptr<resource_ctx_t> &ctx,
 
         dfu_traverser_t &tr = *(ctx->traverser);
 
+        tr.clear_err_message ();
         if (std::string ("allocate") == cmd)
             rc = tr.run (j, ctx->writers, match_op_t::MATCH_ALLOCATE, jobid, at);
         else if (std::string ("allocate_with_satisfiability") == cmd)
@@ -1709,13 +1711,15 @@ static int run (std::shared_ptr<resource_ctx_t> &ctx,
                   static_cast<intmax_t> (jobid));
         goto out;
     }
+    tr.clear_err_message ();
     if ((rc = tr.run (R, ctx->writers, rd, jobid, at, duration)) < 0) {
         flux_log (ctx->h,
                   LOG_ERR,
                   "%s: dfu_traverser_t::run (id=%jd): %s",
                   __FUNCTION__,
                   static_cast<intmax_t> (jobid),
                   ctx->traverser->err_message ().c_str ());
+        ctx->traverser->clear_err_message ();
         goto out;
     }
 
@@ -1909,6 +1913,7 @@ static int run_remove (std::shared_ptr<resource_ctx_t> &ctx,
     int rc = -1;
     dfu_traverser_t &tr = *(ctx->traverser);
 
+    tr.clear_err_message ();
     if (part_cancel) {
         // RV1exec only reader supported in production currently
         std::shared_ptr<resource_reader_base_t> reader;
@@ -1944,6 +1949,7 @@ static int run_remove (std::shared_ptr<resource_ctx_t> &ctx,
                   __FUNCTION__,
                   static_cast<intmax_t> (jobid),
                   ctx->traverser->err_message ().c_str ());
+        ctx->traverser->clear_err_message ();
         goto out;
     }
     if (full_removal && is_existent_jobid (ctx, jobid))
@@ -2676,6 +2682,7 @@ static int run_find (std::shared_ptr<resource_ctx_t> &ctx,
     match_format_t format = match_writers_factory_t::get_writers_type (format_str);
     if (!(w = match_writers_factory_t::create (format)))
         goto error;
+    ctx->traverser->clear_err_message ();
     if ((rc = ctx->traverser->find (w, criteria)) < 0) {
         if (ctx->traverser->err_message () != "") {
             flux_log_error (ctx->h,
@@ -2947,6 +2954,7 @@ static void set_status_request_cb (flux_t *h,
         errmsg = "unrecognized status '" + status + "'";
         goto error;
     }
+    ctx->traverser->clear_err_message ();
     // mark the vertex
     if (ctx->traverser->mark (resource_path, status_it->second) < 0) {
         flux_log_error (h,