T64562: fix Content-Length bug

For files with a length larger than a signed 32-bit integer (about 2 gigs) there is a Java bug that results in Content-Length being set to 0. Normally this doesn't cause a problem (e.g., vcp has no problem copying large files). However, vofs needs to know this length, and reading such a large file causes an exception. The first commit is an updated integration test that demonstrates the problem. The second commit uses the accepted workaround of using X_CADC-Content-Length as a fallback.

Question: is something similar needed for puts with vofs?