fix beta labs puppet fail monitoring

thanks to Yuvi we have this new check for
puppet failures on instances in beta labs
which shows up in Icinga now [1]

but: the output is currently "NULL" and status
     is CRITICAL

when using "min" instead of "m" and a positive value
for the from parameter it works though:


@neon:/usr/lib/nagios/plugins# ./check_graphite -U 
http://labmon1001.eqiad.wmnet -T 10 check_threshold 'deployment-
prep.*.puppetagent.failed_events.value' -W 1 -C 1 --from 10min
--perc 1 --over

OK: Less than 1.00% above the threshold [1.0]



[1] https://icinga.wikimedia.org/cgi-bin/icinga
/status.cgi?host=labmon1001&nostatusheader

Change-Id: I4dfa90380558c99b9d629b628dc223f9537c8ab2