engine: GetSubsystemsStatus fix (#773)

* engine: GetSubsystemsStatus fix

* engine: force map literal to stop doubling up on keys, expanded test coverage

* engine: Deploy default for migration requirement.

* glorious: nits addr

* glorious: suggestion

* tests: fix

engine/connection_manager.go

@@ -1,6 +1,7 @@
 package engine
 
 import (
+	"errors"
 	"fmt"
 	"sync/atomic"
 
@@ -12,6 +13,8 @@ import (
 // ConnectionManagerName is an exported subsystem name
 const ConnectionManagerName = "internet_monitor"
 
+var errConnectionCheckerIsNil = errors.New("connection checker is nil")
+
 // connectionManager manages the connchecker
 type connectionManager struct {
 	started int32
@@ -72,14 +75,17 @@ func (m *connectionManager) Start() error {
 // Stop stops the connection manager
 func (m *connectionManager) Stop() error {
 	if m == nil {
-		return fmt.Errorf("connection manager %w", ErrNilSubsystem)
+		return fmt.Errorf("connection manager: %w", ErrNilSubsystem)
 	}
 	if atomic.LoadInt32(&m.started) == 0 {
-		return fmt.Errorf("connection manager %w", ErrSubSystemNotStarted)
+		return fmt.Errorf("connection manager: %w", ErrSubSystemNotStarted)
 	}
 	defer func() {
 		atomic.CompareAndSwapInt32(&m.started, 1, 0)
 	}()
+	if m.conn == nil {
+		return fmt.Errorf("connection manager: %w", errConnectionCheckerIsNil)
+	}
 	log.Debugln(log.ConnectionMgr, "Connection manager shutting down...")
 	m.conn.Shutdown()
 	log.Debugln(log.ConnectionMgr, "Connection manager stopped.")