Fix the conversion of time option in PUTNOTIF from timestamp to cdtime_t

The time parsed in PUTNOTIF, a timestamp, is not converted to cdtime_t.

Reported in the mailing list by George B:

    Hello,
    
    I have configured a simple test notification using the Exec plugin. This works, however, the Time value in the notification message is changed into something strange (1.307) - can anyone suggest why this is happening?
    
    ----
    root@croaker:~# cat /etc/collectd/collectd.conf
    LoadPlugin exec
    
    <Plugin exec>
            NotificationExec "www-data" "/srv/www/notify.sh"
            Exec "www-data" "/srv/www/test.sh"
    </Plugin>
    ----
    
    ----
    root@croaker:~# cat /srv/www/test.sh
    #!/bin/bash
    
    MESSAGE="Some random text"
    SEVERITY="warning"
    TIME=`date +%s`
    
    LINE="PUTNOTIF message=\"$MESSAGE\" severity=$SEVERITY time=$TIME"
    
    echo "$LINE" >> /tmp/out.txt
    
    echo "$LINE"
    ----
    
    ----
    root@croaker:~# cat /srv/www/notify.sh
    #!/bin/bash
    
    echo "$(cat)" >> /tmp/out.txt
    ----
    
    ----
    root@croaker:~# tail -n 5 /tmp/out.txt
    PUTNOTIF message="Some random text" severity=warning time=1403113649
    Severity: WARNING
    Time: 1.307
    
    Some random text
    ----
    
    I am running collectd 5.1.0 (Debian Wheezy).
    
    
    Thanks,
    
    George