No error message when collect logs whose parent folder that has r+x permission

- Version: Logstash 2.1.1
- Operating System: Red Hat 7.1
- Config File (if you have sensitive info, please remove it):
For example, The input file is:
`input {
file {
type => "linux-syslog"
path => [ "/var/log/messages" ]
start_position => "beginning"
}
}`
- Sample Data:
- Steps to Reproduce: 1.make the user that run logstash have no r+x permission to access the folder /var/log/ 2. Run logstash with the example conf file above, logstash can not read the /var/log/messages, but there is no error messages to show this error.

Start with the file input using the supplied configuration and reproduce the case where the Logstash user lacks r+x permission on /var/log. Confirm that /var/log/messages cannot be read and that the completed fix reports an error explaining the permission failure.

Written by the indexing model from the issue text.