fix: reset errors when fallback to list avds from directory

[Fatme]

When there are errors on avdmanager's stderr and no data on avdmanager's stdout, {N} CLI fallback to list avds from directory and returns both devices (from directory) and errors from avdmanager's stderr. However this is incorrect behavior. In case we fallback to list avds from directory, we need to reset errors output.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

When there are errors on avdmanager's stderr and no data on avdmanager's stdout, {N} CLI fallback to list avds from directory and returns both devices (from directory) and errors from avdmanager's stderr

What is the new behavior?

When there are errors on avdmanager's stderr and no data on avdmanager's stdout, {N} CLI fallback to list avds from directory and returns devices (from directory) and no errors

[Fatme]

run ci