fix the config option to remove the ability for users to set their displayname
Replace static usage of OC_Config and OC_Preferences with the injected \OC\ConfigAll
Merge branch 'master' into user-no-change-displayname
Pass config object in testGetHomeNotSupported
Merge pull request #6513 from owncloud/user-no-change-displayname

Re-add the config options to remove the ability for users to change their displayname