check_icmp: keep performance data order in case of none-reachable hosts
For responding hosts nothing changes:
./check_icmp -H 10.0.0.1
OK - 10.0.0.1 rta 0.336ms lost 0%|rta=0.336ms;200.000;500.000;0; rtmax=0.471ms;;;; rtmin=0.000ms;;;; pl=0%;40;80;0;100
In case the host is down, the performance data now contain 'U' according to:
https://www.monitoring-plugins.org/doc/guidelines.html#AEN201
Old:
./check_icmp -H 10.0.0.99
CRITICAL - 10.0.0.99: Host unreachable @ 10.0.1.138. rta nan, lost 100%|pl=100%;40;80;0;100
Old:
./check_icmp -H 10.0.0.99
CRITICAL - 10.0.0.99: Host unreachable @ 10.0.1.138. rta nan, lost 100%|rta=U;;;; rtmax=U;;;; rtmin=U;;;; pl=100%;40;80;0;100
This confuses some performance graphing tools, ex.: pnp.
Signed-off-by: Sven Nierlein <sven@consol.de>