TESTS: Add files provider integration tests Implements integration tests for the files provider. In order to change entries in the nss-wrapped passwd and group files, this commit also implements a helper module that creates a new passwd and group file and moves it in place of the nss-wrapped files. We move the files instead of modifying them in-place in order to trigger similar inotify notifications as shadow-utils would. The unit test uses sleep on several places. This is suboptimal, but during testing especially on slow machines, it became apparent that sometimes the inotify message arrives later than the test would check for the changed entries. Therefore, the check would query the NSS responder even before the sss-files domain was invalidated. Reviewed-by: Pavel Březina <pbrezina@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>