MFC r315641,r315642:

MFC r315641,r315642:

r315641:

bsnmp: don't leak snmp_client.fd in open_client_udp(..) on connect(2) failure

r315642:

bsnmp: explicitly test the return value for open_client_{local,udp} in snmp_open(..)

open_client_* returns -1 on failure; 0 on success. Ensure that the return value is
0 -- otherwise exit snmp_open(..).

git-svn-id: svn://svn.freebsd.org/base/stable/10@316044 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f