Added memremaining tag

        # we must refresh those tags only when domains tags are registered to

        # have the calculated values

        for tag in ('cpualloc', 'cpurunning', 'memalloc', 'memrunning'):

        for tag in ('cpualloc', 'cpurunning', 'memalloc', 'memrunning', 'memremaining'):

            self.tag_db['__main__'][tag].update_value()

        # register libvirt handlers

import libvirt

from cloudcontrol.node.utils import and_

from cloudcontrol.common.client.tags import ttl, refresh

logger = logging.getLogger(__name__)

    """Memory used by all VMs on the hypervisor."""

    return sum(int(vm.tag_db['__main__']['mem'].value) for vm in

               handl.hypervisor.domains.itervalues() if vm.tag_db['__main__']['mem'].value)

@_check_virt_connected

def memremaining(handl):

    """Allocatable memory remaining on the hypervisor."""

    mem = int(handl.tag_db['__main__']['mem'].value)

    memalloc = int(handl.tag_db['__main__']['memalloc'].value)

    return mem - memalloc

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