bitbake: fetch2: do not suffix srcrev cache key with PN

Prior to this change, two different recipes pulling from the same
exact repo could get a different SRCREV during a single parse session.

This was originally observed using git. For git at least, it still
allows recipes to pull from the same repo, but with different branches
or tags, since the form of the srcrev cache key for git is:

        "git:" + ud.host + ud.path.replace('/', '.') + ud.unresolvedrev[name]

Where the 'unresolvedrev' part is the branch or tag name.

(Bitbake rev: 6c938e6fd29beebe09b32be839dae008fe6491d2)

Signed-off-by: Chris Laplante <chris.laplante@agilent.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/fetch2/__init__.py

@@ -1567,8 +1567,7 @@ class FetchMethod(object):
         return True, str(latest_rev)
 
     def generate_revision_key(self, ud, d, name):
-        key = self._revision_key(ud, d, name)
-        return "%s-%s" % (key, d.getVar("PN") or "")
+        return self._revision_key(ud, d, name)
 
     def latest_versionstring(self, ud, d):
         """