check_snmp calls snmpget without '-c' parameter, which is mandatory
with NetSNMP 5.x. Add '-c' to the command line to make it work with
both NetSNMP 4.x and 5.x.
check_by_ssh dumps core with called without -C, also usage help output
does not document -C and -v.
check_ssh plugin incorrectly parses the SSH banner.
check_ntp does not work with NTP v2. Add -n option to be able to
select NTP version.
Submitted by: David Douthitt <n9ubh@callsign.net>,
Jens Trzaska <jt@barfoos.de> (check_snmp) via maintainer
