sstate.bbclass: Improve stamp-extra-info task handling to avoid warnings

sstate.bbclass: Improve stamp-extra-info task handling to avoid warnings

If you change a machine to a different package architecture, you will see sstate
errors about overwriting files as the code stands today. Instead it should clean
out the files safely and correctly. This patch changes the naming of stamp-extra-info
manifest files to avoid this problem. It will potentially trigger warnings during
builds in existing TMPDIRs until the system adjusts to the new naming, these are
harmless.

[YOCTO #3521]

(From OE-Core rev: 2cc8ee57f8148844bb7bcd4aaf34f6891cf3d410)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>