Change /unload to not wait for inflight requests (#125)

Sometimes upstreams can accept HTTP but never respond causing requests
to build up waiting for a response. This can block Process.Stop() as
that waits for inflight requests to finish. This change refactors the
code to not wait when attempting to shutdown the process.

proxy/processgroup_test.go

@@ -46,7 +46,7 @@ func TestProcessGroup_HasMember(t *testing.T) {
 
 func TestProcessGroup_ProxyRequestSwapIsTrue(t *testing.T) {
 	pg := NewProcessGroup("G1", processGroupTestConfig, testLogger, testLogger)
-	defer pg.StopProcesses()
+	defer pg.StopProcesses(StopWaitForInflightRequest)
 
 	tests := []string{"model1", "model2"}
 
@@ -74,7 +74,7 @@ func TestProcessGroup_ProxyRequestSwapIsTrue(t *testing.T) {
 
 func TestProcessGroup_ProxyRequestSwapIsFalse(t *testing.T) {
 	pg := NewProcessGroup("G2", processGroupTestConfig, testLogger, testLogger)
-	defer pg.StopProcesses()
+	defer pg.StopProcesses(StopWaitForInflightRequest)
 
 	tests := []string{"model3", "model4"}