Comment # 2 on bug 1218872 from Hu

Since you are using a non-default path, I think the right way is to add the
file context via semanage, as you already tried to do. I think semanage can set
the file context to <<none>> though. Try using this on your custom directory
/srv/foo before running your commands:

semanage fcontext -a -t '<<none>>' '/srv/foo/\.snapshots/[^/]*/snapshot(/.*)?'
semanage fcontext -a -t 'snapperd_data_t' '/srv/foo/\.snapshots(/.*)?'

I think that should resolve your issue as this then should not relabel the
snapshot content. 
Please let me know if your issue still persists, thanks!