Bug 1335309 - Change the default for find_executables to False. r=mshal

Back when the class was written, for the packaging code, it made sense
that the default was True. But now that it's used all over the place,
and that the vast majority of uses are with find_executables=False, it
makes more sense for that to be the default.

python/mozbuild/mozpack/files.py

@@ -841,7 +841,7 @@ class FileFinder(BaseFinder):
     '''
     Helper to get appropriate BaseFile instances from the file system.
     '''
-    def __init__(self, base, ignore=(),
+    def __init__(self, base, find_executables=False, ignore=(),
                  find_dotfiles=False, **kargs):
         '''
         Create a FileFinder for files under the given base directory.
@@ -856,8 +856,6 @@ class FileFinder(BaseFinder):
         to a directory, all files under that directory will be ignored. If
         an entry corresponds to a file, that particular file will be ignored.
         '''
-        assert 'find_executables' in kargs
-        find_executables = kargs.pop('find_executables')
         BaseFinder.__init__(self, base, **kargs)
         self.find_dotfiles = find_dotfiles
         self.find_executables = find_executables