Simplify the checkInstanceMove function
Simplify the checkInstanceMove function

This patch flattens the two folds into one, by simply building the whole
list of moves instead  of the double recursion (nodes and the each
node's moves). This has no functional change, but it's much cleaner.
ganeti-github-testing/ganeti-test-1,ganeti/ganeti,dimara/ganeti,andir/ganeti,onponomarev/ganeti,andir/ganeti,yiannist/ganeti,yiannist/ganeti,mbakke/ganeti,leshchevds/ganeti,dimara/ganeti,leshchevds/ganeti,mbakke/ganeti,andir/ganeti,mbakke/ganeti,bitemyapp/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,apyrgio/snf-ganeti,bitemyapp/ganeti,apyrgio/ganeti,leshchevds/ganeti,onponomarev/ganeti,grnet/snf-ganeti,grnet/snf-ganeti,ganeti/ganeti,apyrgio/ganeti