修复由于应用SDK版本问题导致应用无法自升级问题(临时修复方法)

系统集成应用版本升级不成功，查看系统日志Package com.xiaoji.emulator new target SDK 22 doesn’t support runtime permissions but the old target SDK 23 does
应用新版本sdk比旧版本低导致升级失败，从Android6.0之后的版本 targetSDKVerssion是不能降级的.
临时修复方法，在PackageManagerService.java中针对该应用不比较升级应用和原应用的sdk版本，具体修改方法如下

PackageManagerService.java

                if (replace) {
                    // Prevent apps opting out from runtime permissions
                    PackageParser.Package oldPackage = mPackages.get(pkgName);
                    final int oldTargetSdk = oldPackage.applicationInfo.targetSdkVersion;
                    final int newTargetSdk = pkg.applicationInfo.targetSdkVersion;
                    Log.d("test","package =" + pkg.packageName);
                    //modify to fix xiaoji upgrade bug
                    if (oldTargetSdk > Build.VERSION_CODES.LOLLIPOP_MR1
                            && newTargetSdk <= Build.VERSION_CODES.LOLLIPOP_MR1 && !(pkg.packageName.equals("com.xiaoji.emulator"))) {
                        res.setError(PackageManager.INSTALL_FAILED_PERMISSION_MODEL_DOWNGRADE,
                                "Package " + pkg.packageName + " new target SDK " + newTargetSdk
                                        + " doesn't support runtime permissions but the old"
                                        + " target SDK " + oldTargetSdk + " does.");
                            return;
                    }

                    // Prevent installing of child packages
                    if (oldPackage.parentPackage != null) {
                        res.setError(PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME,
                                "Package " + pkg.packageName + " is child of package "
                                        + oldPackage.parentPackage + ". Child packages "
                                        + "can be updated only through the parent package.");
                        return;
                    }
                }
            }