Use FileSnapshot without using configs for FileBasedConfig

Use FileSnapshot without using configs for FileBasedConfig

FileBasedConfig should not rely on auto-detection of
the file-snapshot attribute computation based on config.

The check was already performed when a new FileBasedConfig
is created at L158:

// don't use config in this snapshot to avoid endless recursion
newSnapshot = FileSnapshot.saveNoConfig(getFile());

The check was missing though when the FileBasedConfig is saved
to disk and the new snapshot is obtained from the associated
LockFile.

This change fixes the issue by keeping a non-config based
FileSnapshot also after a FileBasedConfig is saved.

Bug: 577983
Change-Id: Id1e410ba687e683ff2b2643af31e1110b103b356