net-snmp: split net-snmp-server

net-snmp-server has been split into two packages:
net-snmp-server-snmpd and net-snmp-server-snmptrapd

net-snmp-server is now a "meta-package" which depends on
net-snmp-server-snmpd and net-snmp-server-snmptrapd.

net-snmpd-server-systemd in no longer generated.  It has been
split into net-snmp-server-snmpd-systemd and
net-snmp-server-snmptrapd-systemd.

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>