PR #6366 implemented a tree-wide change to replace github.com/pkg/errors
to errors. The new sandbox API PR #6703 had few errors.Wrap*() leftovers
and pulled github.com/pkg/errors back. This commit replaces those
leftovers by following the pattern in #6366.
Signed-off-by: Mikko Ylinen <mikko.ylinen@intel.com>