MantaHTTPSuite needs updating for new router

[chorrell]

As noted here: #6 (comment)

It's not really clear how the test suite is supposed to be run.

[tgross]

After setting everything up as per the updated README here's what I get:

go test ./...
# github.com/joyent/gomanta/localservices/manta_test
localservices/manta/service_http_test.go:65: cannot use s.HTTPSuite.Mux (type *httprouter.Router) as type *"net/http".ServeMux in argument to s.service.SetupHTTP
ok      github.com/joyent/gomanta       0.006s
?       github.com/joyent/gomanta/localservices [no test files]
ok      github.com/joyent/gomanta/localservices/hook    0.006s
FAIL    github.com/joyent/gomanta/localservices/manta [build failed]
ok      github.com/joyent/gomanta/manta 0.261s

The s object referred to above is a MantaHTTPSuite which embeds the testing.HTTPSuite from our gocommon lib. Looks like the last commit to that lib TritonDataCenter/gocommon@f676d62 updated the routing library, but this consumer was not caught. I'll get this fixed up.