(maint) Switch to stubbing correct object method for corrective_change test
(maint) Switch to stubbing correct object method for corrective_change test

The test was presuming that a report could be modified like an array, but it
really needed the property method. This property is an attr_reader, stubbing
gets around this access problem though.

Signed-off-by: Ken Barber <470bc578162732ac7f9d387d34c4af4ca6e1b6f7@bob.sh>

waynr/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,rbrw/puppetdb,waynr/puppetdb,kbarber/puppetdb,senior/puppetdb,mullr/puppetdb,puppetlabs/puppetdb,kbarber/puppetdb,puppetlabs/puppetdb,mullr/puppetdb,kbarber/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,rbrw/puppetdb,mullr/puppetdb,rbrw/puppetdb,mullr/puppetdb,waynr/puppetdb,senior/puppetdb,mullr/puppetdb,senior/puppetdb,senior/puppetdb,kbarber/puppetdb,puppetlabs/puppetdb,waynr/puppetdb