Fix resolution of Gitlab::AppLogger in EE kerberos_spnego_helper

Since `EE::Gitlab` is already defined we need to fully qualify
`::Gitlab::AppLogger` (non-EE) in `EE` modules.

ee/app/helpers/ee/kerberos_spnego_helper.rb

@@ -82,7 +82,7 @@ module EE
       # Return user principal name if authentication succeeded
       gss.display_name
     rescue GSSAPI::GssApiError => ex
-      Gitlab::AppLogger.error "#{self.class.name}: failed to process Negotiate/Kerberos authentication: #{ex.message}"
+      ::Gitlab::AppLogger.error "#{self.class.name}: failed to process Negotiate/Kerberos authentication: #{ex.message}"
       false
     end
 

ee/spec/helpers/kerberos_spnego_helper_spec.rb

@@ -10,6 +10,7 @@ RSpec.describe KerberosSpnegoHelper do
 
     subject { Class.new { include KerberosSpnegoHelper }.new }
 
+    context 'with successful remote call' do
       before do
         expect(GSSAPI::Simple).to receive(:new)
           .with(nil, nil, ::Gitlab.config.kerberos.keytab)
@@ -60,4 +61,22 @@ RSpec.describe KerberosSpnegoHelper do
         end
       end
     end
+
+    context 'when the remote call fails' do
+      before do
+        allow(GSSAPI::Simple).to receive(:new)
+          .with(nil, nil, ::Gitlab.config.kerberos.keytab)
+          .and_raise(GSSAPI::GssApiError, 'a message')
+
+        allow(Gitlab::AppLogger).to receive(:error).and_call_original
+      end
+
+      it 'fails to authenticate and logs an error' do
+        expect(subject.spnego_credentials!('some token')).to eq(false)
+
+        expect(Gitlab::AppLogger).to have_received(:error)
+          .with(%r{failed to process Negotiate/Kerberos authentication: a message})
+      end
+    end
+  end
 end