Fix checksum of not accessible url using fall back url

[svenjungnickel]

Short description of what this resolves:

This commit addresses a fix for the FileAlreadyExistDecision.php for a not accessible url.

Changes proposed in this pull request:

In case the provided url is not accessible and the downloaded file already exists, a ErrorException sha1_file(http://notaccessible.url/version/tool.phar): failed to open stream: Operation timed out was thrown. This commit fixes this issue by adding an extra check for the accessibility of the url. If the url is not accessible, the fallback url is used for the checksum.

Version: 1.4.0

Fixes: #

[svenjungnickel]

Hey @tommy-muehle, any chance to get this PR merged soon? It fixes an issue in the latest version 1.4.0 with the new fallback url feature. You basically just have to merge and tag a bugfix version :)

[tommy-muehle]

Thanks for the fix. And sorry for the late response!