proxy: improve ABCI app connection handling (#5078)

Closes #5074 

Old code does not work when --consensus.create_empty_blocks=false
(because it only calls tmos.Kill when ApplyBlock fails). New code is
listening ABCI clients for Quit and kills TM process if there were any
errors.

proxy/mocks/client_creator.go

@@ -0,0 +1,36 @@
+// Code generated by mockery v1.1.1. DO NOT EDIT.
+
+package mocks
+
+import (
+	mock "github.com/stretchr/testify/mock"
+	abcicli "github.com/tendermint/tendermint/abci/client"
+)
+
+// ClientCreator is an autogenerated mock type for the ClientCreator type
+type ClientCreator struct {
+	mock.Mock
+}
+
+// NewABCIClient provides a mock function with given fields:
+func (_m *ClientCreator) NewABCIClient() (abcicli.Client, error) {
+	ret := _m.Called()
+
+	var r0 abcicli.Client
+	if rf, ok := ret.Get(0).(func() abcicli.Client); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(abcicli.Client)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func() error); ok {
+		r1 = rf()
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}