Fixed the required_if message replacer

added test to check required_if with multiple values

moved the test to proper method
Make isValid() check only for UploadedFile instances
Merge pull request #5456 from leesherwood/4.2

Make isValid() check only for UploadedFile instances
Merge pull request #5262 from mohitmamoria/4.2

Fixes the required_if messages if multiple values are passed