Fix a bug in getInstalledAccessibilityServiceList()

Steps to reproduce:
1. Run Unit test, such as CTS test:
run cts -c com.android.cts.jank.ui.CtsHostJankUi -m testScrolling
2. Press Home key to go back home screen.
3. Enter Settings->Accessibility at the same time.
Then we can see the Settings force closed.

The UiAutomationService's ResolveInfo is null. AccessibilityManagerService
should not return its AccessibilityServiceInfo to client (such as Settings
app) in getInstalledAccessibilityServiceList() method.
getInstalledAccessibilityServiceList() should have removed the
AccessibilityServiceInfo that for UiAutomationService, but it incorrectly
removes UiAutomationService itself now.

Change-Id: I790d87c7d4bc069d63fe83026b1c8cff8af87ab9
Signed-off-by: hanpengx <pengfeix.han@intel.com>
Signed-off-by: Guobin Zhang <guobin.zhang@intel.com>