Uploading new file to Azure Blob Storage with metadata fails on metadata write

[OJezu]

Gaufrette tries to save metadata before uploading the file itself. Alas, if there is no file before that API call for setting metadata will fail on all providers who don't support setting metadata on non-existent file/blob.

<?php
(...)
        $gaufretteFile = new File($path, $filesystem);
        $gaufretteFile->setContent('content', ['contentType' => 'what/ever']);

results in:

Uncaught PHP Exception RuntimeException: "Failed to set metadata for blob "$path" in container "$container": The specified blob does not exist. (BlobNotFound)."

As can be seen in Gaufrette/File::setContent

        $this->content = $content;
        $this->setMetadata($metadata);

        return $this->size = $this->filesystem->write($this->key, $this->content, true);

setMetadata is causing filesystem beneath to issue a metadata write, which fails.

[xixi773]

This fix works if someone can merge it. =)