tests/avocado: fix tcg_plugin mem access count test

When we cleaned up argument handling the test was missed.

Fixes: 5ae589faad ("tests/plugins/mem: introduce "track" arg and make args not positional")
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20211129140932.4115115-4-alex.bennee@linaro.org>

tests/avocado/tcg_plugins.py

@@ -131,7 +131,7 @@ def test_aarch64_virt_mem_icount(self):
                                                  suffix=".log")
 
         self.run_vm(kernel_path, kernel_command_line,
-                    "tests/plugin/libmem.so,arg=both", plugin_log.name,
+                    "tests/plugin/libmem.so,inline=true,callback=true", plugin_log.name,
                     console_pattern,
                     args=('-icount', 'shift=1'))