Fix caching for installed platforms and libraries

platformio/libmanager.py

@@ -32,7 +32,6 @@ class LibraryManager(object):
         fu = FileUnpacker(pkgpath, dest_dir)
         return fu.start()
 
-    @util.memoized
     def get_installed(self):
         items = {}
         if not isdir(self.lib_dir):

platformio/platforms/base.py

@@ -132,7 +132,6 @@ class PlatformFactory(object):
         return module
 
     @classmethod
-    @util.memoized
     def _lookup_platforms(cls):
         platforms = {}
         for d in (util.get_home_dir(), util.get_source_dir()):