Re: Calling PrepareTempTablespaces in BufFileCreateTemp

There are three functions in fd.c that have a dependency on the
temp tablespace info having been set up:
        OpenTemporaryFile
        GetTempTablespaces
        GetNextTempTableSpace
This patch makes the first of those automatically set up the info
if it's not done yet.  The second one has always had an assertion
that the caller did it already, and now the third one does too.
An about equally plausible change would be to make all three
call PrepareTempTablespaces, but there are so few callers of the
second and third that I'm not sure that'd be better.  Thoughts?