Fix mistake in Pytables querying with numpy scalar value.  Fixes #11283
Fixes #11283

First PR to this project.  The fix is minuscule, but let me know if I did anything awry.

Could you please add a note to the bug fixes section of the release notes?
https://github.com/pydata/pandas/blob/master/doc/source/whatsnew/v0.17.1.txt

Also, be sure to include `Fixes #XXXX` in the body of your comment in pull requests -- that links the issues and will automatically close it when the PR is merged (I just edited your message to add that in).
 lgtm. pls squash. ping on green.
 @jreback Are you saying to do `rhs = np.array(rhs)` instead of `rhs = [rhs]`?  As far as I can tell that line is only to make the iteration work right in the line right after the call to `conform` ([here](https://github.com/pydata/pandas/blob/c2aa6a2333483d0e95661c34de360dbcdc8d1bba/pandas/computation/pytables.py#L249)).  I don't think it needs to be a numpy array and I'm a bit reluctant to make that change without knowing why.  It doesn't appear to be causing any problems.

The fix is working fine now.
 thanks
