RUBY-2445 retry the test to fight flakiness (#2342)

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

spec/mongo/client_construction_spec.rb

@@ -447,7 +447,7 @@
             end.should_not raise_error
           end
 
-          it 'fails operations due to very small timeout' do
+          it 'fails operations due to very small timeout', retry: 3 do
             lambda do
               client.database.command(ping: 1)
             end.should raise_error(Mongo::Error::SocketTimeoutError)