Fix NagiosCfg lense so /etc/nagios/nrpe.cfg is parsed by Nrpe and not NagiosCfg

Currently NagiosCfg lense is in charge of parsing all files under /etc/nagios/*.cfg
but /etc/nagios/commands.cfg. /etc/nagios/nrpe.cfg should be also added as an exception
since it needs to be parsed by the Nrpe lense. This issue currently causes the following
error : "Lenses @NagiosCfg and @Nrpe could be used to load this file"
Fix Trac#364. Syslog lense accept UDP(@) and TCP(@@) protocol

Currently the syslog lense only accept sending log to another host
via UDP - a single @ -, and was discarding TCP - a double @ -. This
PR fixes that.

Fix test_rsyslog.aug

Remove unused variable at
Added dhclient.conf path for Debian/Ubuntu
Exports: permit colons for IPv6 client addresses

Fixes ticket #366
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