MEDIUM: dns: Add resolve-opts "ignore-weight"

MEDIUM: dns: Add resolve-opts "ignore-weight"

It was noted in #48 that there are times when a configuration
may use the server-template directive with SRV records and
simultaneously want to control weights using an agent-check or
through the runtime api.  This patch adds a new option
"ignore-weight" to the "resolve-opts" directive.

When specified, any weight indicated within an SRV record will
be ignored.  This is for both initial resolution and ongoing
resolution.