MFC 224495:

MFC 224495:
Properly initialize an error variable to avoid returning uninitialized
data when 'show drives' succeeds, often resulting in a failing exit code
even though the command worked fine.

git-svn-id: svn://svn.freebsd.org/base/stable/8@225084 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f