Adding a wait for device ready before deleting packages. (flutter#3167)

Adding an additional wait, since we experienced a package manager not ready error.

Bug:flutter/flutter#135035

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*List which issues are fixed by this PR. You must list at least one issue.*

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cipd_packages/device_doctor/lib/src/android_device.dart

@@ -453,6 +453,8 @@ class AndroidDevice implements Device {
     processManager ??= LocalProcessManager();
     final int timeoutSecs = 60;
     print('Device recovery: deleting package caches...');
+    await eval('adb', <String>['wait-for-device'], canFail: false, processManager: processManager)
+        .timeout(Duration(seconds: timeoutSecs));
     await deletePackageCache();
     await eval('adb', <String>['wait-for-device'], canFail: false, processManager: processManager)
         .timeout(Duration(seconds: timeoutSecs));