Revert "configure: try to use -Wl,--as-needed if possible"

Revert "configure: try to use -Wl,--as-needed if possible"

This reverts commit 01b911bccfa29435929665c7df827f70de36ccfa. On some
systems, netsnmpagent is not linked to all required libs.

undefined symbol: netsnmpUDPDomain(/usr/lib/libnetsnmpagent.so.9)
undefined symbol: vacm_parse_config_group(/usr/lib/libnetsnmpagent.so.9)
undefined symbol: netsnmp_TCPIPv6Domain(/usr/lib/libnetsnmpagent.so.9)
undefined symbol: snmp_errno(/usr/lib/libnetsnmpagent.so.9)
[...]

Therefore, we really need to really need to link to some libraries
present in net-snmp-config.