Move unpacking of config-change to a separate function
Move unpacking of config-change to a separate function

In this way, the logic of determining whether the configuration needs
to be distributed, as well as the implicit serial numb can be shared
with other functions.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Aaron Karper <99cc1031546340b2b8ced5fe338b5890677a56ca@google.com>

ganeti/ganeti,andir/ganeti,yiannist/ganeti,bitemyapp/ganeti,yiannist/ganeti,mbakke/ganeti,apyrgio/ganeti,grnet/snf-ganeti,andir/ganeti,dimara/ganeti,onponomarev/ganeti,leshchevds/ganeti,apyrgio/ganeti,ganeti/ganeti,andir/ganeti,mbakke/ganeti,onponomarev/ganeti,ganeti/ganeti,bitemyapp/ganeti,dimara/ganeti,grnet/snf-ganeti,mbakke/ganeti,yiannist/ganeti,leshchevds/ganeti,leshchevds/ganeti