Add utils.{Write,Remove}PidFile
Add utils.{Write,Remove}PidFile

WritePidFile is a helper function that writes the current pid in a
pidfile within the ganeti run directory. RemovePidFile tries to delete
it.

Reviewed-by: iustinp



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