build: add command check-clean

This command will package the clean operations in tests. Now root Makefile
simply calls the command and do not care the details of it any more. Original
the built binaries for test will not be removed, now they will be deleted
in clean operation.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
