How to avoid Forced reboots using unattended upgrades to SQL Server 2014

Upgrading seven instances from SQL Server 2008R2 to 2014 via the command line using a configuration file. The upgrade runs fine but when I move on to upgrading the next instance I get the following error.

From : C:\Program Files\Microsoft SQL Server\120\Setup Bootstrap\Log\20150105_152519\Summary.txt

Error result: -2067919934
Result facility code: 1214
Result error code: 3010

Exception type: Microsoft.SqlServer.Configuration.RulesEngineExtension.RulesEngineRuleFailureException
    Message: 
        A computer restart is required. You must restart this computer before installing SQL Server.
    HResult : 0x84be0bc2
        FacilityCode : 1214 (4be)
        ErrorCode : 3010 (0bc2)
    Data: 
      SQL.Setup.FailureCategory = RuleViolationFailure
      DisableWatson = true
    Stack: 
        at Microsoft.SqlServer.Configuration.RulesEngineExtension.RunRulesAction.ExecuteAction(String actionId)
        at Microsoft.SqlServer.Chainer.Infrastructure.Action.Execute(String actionId, TextWriter errorStream)
        at Microsoft.SqlServer.Setup.Chainer.Workflow.ActionInvocation.<>c__DisplayClasse.<ExecuteActionWithRetryHelper>b__b()
        at Microsoft.SqlServer.Setup.Chainer.Workflow.ActionInvocation.ExecuteActionHelper(ActionWorker workerDelegate)

I am able to continue after restarting, but something is very wrong if I have to restart after every upgrade. Can someone help me figure out, why I have to restart after upgrading every instance?

Here is the configuration file I'm using

INSTANCENAME="SOME_INSTANCE"
SQMREPORTING="False"
INSTANCEID="SOME_INSTANCE"
IACCEPTSQLSERVERLICENSETERMS="True"
ACTION="Upgrade"
ENU="True"
QUIET="True"
UpdateEnabled="True"
ERRORREPORTING="False"
USEMICROSOFTUPDATE="False"
UpdateSource="MU"
HELP="False"
INDICATEPROGRESS="False"
X86="False"
FAILOVERCLUSTERROLLOWNERSHIP="2"

Here is the command being used to upgrade :

setup.exe  /ConfigurationFile="Confguration_Upgrade.ini"