Also fix BE ut:
1. fix scheme_change_test memory leak
2. fix mem_pool_test
Do not using DEFAULT_PADDING_SIZE = 0x10 in mem_pool when running ut.
3. remove plugin_test
Also fix BE ut:
1. fix scheme_change_test memory leak
2. fix mem_pool_test
Do not using DEFAULT_PADDING_SIZE = 0x10 in mem_pool when running ut.
3. remove plugin_test