MDEV-33582 Add more warnings to be able to better diagnose network issues

Changed the logged messages from errors to warnings
Also changed 'remain' to 'read_length' in the warning to make it more readable.

mysql-test/suite/rpl/r/rpl_semi_sync_cond_var_per_thd.result

@@ -2,6 +2,9 @@ include/master-slave.inc
 [connection master]
 connection master;
 call mtr.add_suppression("Got an error reading communication packets");
+call mtr.add_suppression("Got an error writing communication packets");
+call mtr.add_suppression("Could not read packet");
+call mtr.add_suppression("Could not write packet");
 set @save_bgc_count= @@global.binlog_commit_wait_count;
 set @save_bgc_usec= @@global.binlog_commit_wait_usec;
 set @save_debug_dbug= @@global.debug_dbug;

mysql-test/suite/rpl/t/rpl_semi_sync_cond_var_per_thd.test

@@ -26,6 +26,9 @@
 
 --connection master
 call mtr.add_suppression("Got an error reading communication packets");
+call mtr.add_suppression("Got an error writing communication packets");
+call mtr.add_suppression("Could not read packet");
+call mtr.add_suppression("Could not write packet");
 set @save_bgc_count= @@global.binlog_commit_wait_count;
 set @save_bgc_usec= @@global.binlog_commit_wait_usec;
 set @save_debug_dbug= @@global.debug_dbug;

sql/net_serv.cc

@@ -778,13 +778,12 @@ net_real_write(NET *net,const uchar *packet, size_t len)
 #ifdef MYSQL_SERVER
       if (global_system_variables.log_warnings > 3)
       {
-        my_printf_error(net->last_errno,
-                        "Could not write packet: fd: %lld  state: %d  "
+        sql_print_warning("Could not write packet: fd: %lld  state: %d  "
                           "errno: %d  vio_errno: %d  length: %ld",
-                        MYF(ME_ERROR_LOG),
+                          MYF(ME_ERROR_LOG | ME_WARNING),
                           (longlong) vio_fd(net->vio), (int) net->vio->state,
-                        vio_errno(net->vio), net->last_errno, (ulong) (end-pos));
-        break;
+                          vio_errno(net->vio), net->last_errno,
+                          (ulong) (end-pos));
       }
 #endif
       MYSQL_SERVER_my_error(net->last_errno, MYF(0));
@@ -1101,16 +1100,15 @@ my_real_read(NET *net, size_t *complen,
 #ifdef MYSQL_SERVER
           if (global_system_variables.log_warnings > 3)
           {
-            my_printf_error(net->last_errno,
-                            "Could not read packet: fd: %lld  state: %d  "
-                            "remain: %u  errno: %d  vio_errno: %d  "
+            /* Log things as a warning */
+            sql_print_warning("Could not read packet: fd: %lld  state: %d  "
+                              "read_length: %u  errno: %d  vio_errno: %d  "
                               "length: %lld",
-                            MYF(ME_ERROR_LOG),
-                            (longlong) vio_fd(net->vio), (int) net->vio->state,
+                              (longlong) vio_fd(net->vio),
+                              (int) net->vio->state,
                               remain, vio_errno(net->vio), net->last_errno,
                               (longlong) length);
           }
-          else
           my_error(net->last_errno, MYF(0));
 #endif /* MYSQL_SERVER */
 	  goto end;