coredumpctl: Don't treat no coredumps as failure

Having to deal with a process that fails or doesn't fail depending on
whether there are coredumps or not is incredibly annoying for users.

man/coredumpctl.xml

@@ -389,10 +389,7 @@
 
   <refsect1>
     <title>Exit status</title>
-    <para>On success, 0 is returned; otherwise, a non-zero failure
-    code is returned. Not finding any matching core dumps is treated as
-    failure.
-    </para>
+    <para>On success, 0 is returned; otherwise, a non-zero failure code is returned.</para>
   </refsect1>
 
   <refsect1>

src/coredump/coredumpctl.c

@@ -963,9 +963,10 @@ static int dump_list(int argc, char **argv, void *userdata) {
                 }
 
                 if (!arg_field && n_found <= 0) {
-                        if (!arg_quiet)
+                        if (!arg_quiet && !sd_json_format_enabled(arg_json_format_flags))
                                 log_notice("No coredumps found.");
-                        return -ESRCH;
+
+                        return 0;
                 }
         }