Fix coverity defects: CID 176037

CID 176037: Uninitialized scalar variable

This patch fixes an uninitialized variable defect caught by
coverity and introduced in 69830602

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #7667