Broken indent everywhere except the first open buffer

[liskin]

indent/python.vim is only executed once per vim instance: https://github.com/bazelbuild/vim-ft-bzl/blob/941fb142f604c254029c2a0852ea7578f08de91a/indent/bzl.vim#L23-L25 but it should really be executed once per buffer, because it sets autoindent and GetPythonIndent (actually python#GetIndent these days) relies on autoindent being set.

In other words, bzl indenting only works in the first bzl buffer, provided no python buffer was opened before. If it was, it doesn't even work there.