Improve dn_matches_filter method

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

lib/gitlab/ldap/adapter.rb

@@ -107,12 +107,7 @@ module Gitlab
       end
 
       def dn_matches_filter?(dn, filter)
-        results = ldap_search(base: dn, filter: filter, attributes: %w{dn})
-        if results.blank?
-          false # Net::LDAP encountered an LDAP error
-        else
-          results.any?
-        end
+        ldap_search(base: dn, filter: filter, attributes: %w{dn}).any?
       end
 
       def ldap_search(*args)

spec/lib/gitlab/ldap/ldap_adapter_spec.rb

@@ -23,7 +23,7 @@ describe Gitlab::LDAP::Adapter do
     end
 
     context "when the search encounters an error" do
-      before { ldap.stub(search: nil) }
+      before { ldap.stub(search: nil, get_operation_result: double(code: 1, message: 'some error')) }
 
       it { should be_false }
     end