sstate-cache-management.sh: fix remove_duplicated when multiple archs were built

sstate-cache-management.sh: fix remove_duplicated when multiple archs were built

* The problem is that you're looking for duplicates across all available archs, so
  armv4t and armv7a populate_sysroot are considered duplicate and only last one is
  kept, but to rebuild from sstate-cache you need both!

(From OE-Core rev: 46309e96300c35f6e8a5f33512a6a38720c629d2)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>