net-snmp: fix mib representation of timeout values

Fix mib representation of timeout values,correct conversion
factor from microseconds to centiseconds.

Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>