bitbake: data_smart: Ensure hash reflects vardepvalue flags correctly

The get_hash() function is used to decide if the base configuration has changed
and hence whether a reparse is required. The vardepvalue flag's value was not
expanded but it is often used in contexts like:

METADATA_REVISION = "${@base_detect_revision(d)}"
METADATA_REVISION[vardepvalue] = "${METADATA_REVISION}"

which in it's unexpanded form means reparsing doesn't happen when it should
as the data appears unchanged. Update get_hash to expand the values of
vardepvalue so reparsing works as expected. This avoids basehash mismatch
errors such as the one recently caused by using METADATA_REVISION in poky.conf's
DISTRO_VERSION variable. The issue there could be exposed by a recipe using
DISTRO_VERSION with the sequence:

bitbake os-release
<change the revision of the metadata with a dummy commit>
bitbake os-release -C install

which was caused because METADATA_REVISION changed but the metadata didn't reparse.

(Bitbake rev: 26ccf1575aef2d6e2d7717d3bd10b1ed0d5a777d)

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

bitbake/lib/bb/data_smart.py

@@ -1005,7 +1005,7 @@ class DataSmart(MutableMapping):
             else:
                 data.update({key:value})
 
-            varflags = d.getVarFlags(key, internalflags = True)
+            varflags = d.getVarFlags(key, internalflags = True, expand=["vardepvalue"])
             if not varflags:
                 continue
             for f in varflags: