ganeti-watcher: Don't write file if data didn't change
ganeti-watcher: Don't write file if data didn't change

This is the safest way to detect changes and the amount of data
is small, so keeping a copy around is cheap enough.

Reviewed-by: iustinp


ganeti/ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,mbakke/ganeti,leshchevds/ganeti,apyrgio/snf-ganeti,andir/ganeti,grnet/snf-ganeti,apyrgio/ganeti,yiannist/ganeti,mbakke/ganeti,dimara/ganeti,ganeti/ganeti,yiannist/ganeti,leshchevds/ganeti,andir/ganeti,apyrgio/ganeti,dimara/ganeti,onponomarev/ganeti,andir/ganeti,bitemyapp/ganeti,onponomarev/ganeti,bitemyapp/ganeti,yiannist/ganeti,apyrgio/snf-ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1,grnet/snf-ganeti