CredentialsV3: Ensure all attributes are cleared by unset

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

lib/puppet/provider/openstack/credentials.rb

@@ -45,10 +45,10 @@ class Puppet::Provider::Openstack::Credentials
   end
 
   def unset
-    KEYS.each do |key|
-      if key != :identity_api_version &&
-        self.instance_variable_defined?("@#{key}")
-        set(key, '')
+    self.instance_variables.each do |var|
+      if var.to_s != '@identity_api_version' &&
+        self.instance_variable_defined?(var.to_s)
+        set(var.to_s.sub(/^@/,''), '')
       end
     end
   end

spec/unit/provider/openstack/credentials_spec.rb

@@ -86,6 +86,7 @@ describe Puppet::Provider::Openstack::Credentials do
         creds.auth_url = 'auth_url'
         creds.password = 'password'
         creds.project_name = 'project_name'
+        creds.domain_name = 'domain_name'
         creds.username = 'username'
         creds.token = 'token'
         creds.endpoint = 'endpoint'
@@ -94,6 +95,7 @@ describe Puppet::Provider::Openstack::Credentials do
         expect(creds.auth_url).to eq('')
         expect(creds.password).to eq('')
         expect(creds.project_name).to eq('')
+        expect(creds.domain_name).to eq('')
         expect(creds.username).to eq('')
         expect(creds.token).to eq('')
         expect(creds.endpoint).to eq('')