package.bbclass: Fix populate_packages for glob expansion issues

If we put a valid glob like "*/foo/*" into FILES, populate_packages breaks with a "file exists" message. This is because the glob expansion does not have "./" prefix however there may already be an entry in the seen list which does have such a prefix. The easiest/simplest fix right now is to add the prefix if it doesn't exist which only happens for certain globs.

(From OE-Core rev: 3c6b1730412e3c5b6f628a70b854c0631e7bd9dc)

---

index 4e9b79e..5765e12 100644
@@ -946,6 +946,8 @@ python populate_packages () {
         for file in files:
             if os.path.isabs(file):
                 file = '.' + file
+            if not file.startswith("./"):
+                file = './' + file
             if not cpath.islink(file):
                 if cpath.isdir(file):
                     newfiles =  [ os.path.join(file,x) for x in os.listdir(file) ]