Check file permissions before starting server

[adishegde]

Currently, read and write permissions are not being checked for any file-based operation. Availability of permissions needs to be checked for the following:

• [x] Meta data database
• [x] File indexing
• [x] HTTP service
• [x] Log files
• [x] Config file

There might not be a need to restrict or change many of the above services. But it needs to be verified nevertheless.

[adishegde]

For metadata database and config file, the method recommended in docs has been used i.e. read and write should be done with error handling rather than calling fs.access.