check upload dir permissions
Created by: bbodenmiller
Detect permission and ownership issues with the users uploads dir. This helps troubleshoot and correct omnibus issue 311. Fixes https://github.com/gitlabhq/gitlabhq/issues/7500, https://github.com/gitlabhq/gitlabhq/issues/7052. Related to https://github.com/gitlabhq/gitlabhq/issues/6281.