global name 'saneWhich' is not defined

[JonnyJD]

reported by @jesus2099 in #33 (comment)

I have a global name 'saneWhich' is not defined error when I try to use cdrdao.

hasBackend() is used when checking for a backend given as option before saneWhich is defined.

[JonnyJD]

I could move saneWhich further up on global space, or maybe it would be better to make it a function (caching a global or not).