Currently the unset method only clears attributes defined in the base
Crednetial class and ones specific to CredentialV3 are left set.
This change ensures the method clears all attributes.
Closes-Bug: #1942145
Change-Id: I4bddbf9bb3c6251aa8b68a8bc2ef8799f3c8065e
(cherry picked from commit d1eb834a20)