In
54deb01f00 vfs: Make OpenFile and friends return EINVAL if O_RDONLY and O_TRUNC
The generated file open_test.go was edited directly without editing
the generator.
This commit brings the generator make_open_tests.go back into line
with that edit. It also makes it so `go generate` can be used to
regenerate the tests.
Before this change, renaming and deleting of open files (which can
easily happen due to the asynchronous nature of file systems) would
produce an error, for example saving files with Firefox.
After this change we open files with the flags necessary for open
files to be renamed or deleted.
Fixes#2730
