Remove uneeded code from pkg-map

This patch removes a couple of lines of redundant code.  In Python,
the get method on a dictionary defaults the return value to None,
so the method never raises a key error.

https://docs.python.org/2/library/stdtypes.html#typesmapping

Change-Id: I180877f9be23d373cd63771bb3682d6587ec6fac

elements/pkg-map/bin/pkg-map

@@ -89,9 +89,7 @@ def main():
         if distro_map:
             name_map.update(distro_map)
     for name in extra:
-        pkg_name = None
-        if name in name_map:
-            pkg_name = name_map.get(name)
+        pkg_name = name_map.get(name)
         if pkg_name:
             print(pkg_name)
         else: