Show ext version status even when directory not writeable

[colemanw]

Overview

Gives information about extension updates even if the extension directory is not writable.

Before

If the extension directory was not writable, the system check would return early and not check for available updates.

After

System status page shows available updates regardless.

[civibot]

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[colemanw]

@mlutfy could you review this one please? I specifically did it for civicrm.org, where the directory is not writable and we don't get any extension upgrade notices.

[mlutfy]

Thanks @colemanw, I confirm that this fixes the issue. From code review, seems like a reasonable and safe change, with no impact on other users.