Add utils.CheckBEParams
Add utils.CheckBEParams

This function will be used in LUCreateInstance, LUSetInstanceParams,
LUSetClusterParams and InitCluster to check the backend parameters
validity and convert the relevant values to integer, without duplicating
code. It lives in utils as bootstrap.py is calling it too.

Reviewed-by: imsnah


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