Auto-delete checksum files

In this release, gridftp-hdfs can be set to cleanup checksum files when a file is deleted via GridFTP.

To enable this feature, set GRIDFTP_HDFS_CHECKSUMS_CLEANUP=1 in the sysconfig or systemd-based environment overrides. The default behavior is to keep the checksum files.

Thanks to @jthiltges for this much-requested feature!

Bugfixes for checksum generation

This release fixes a potential double-free that may occur when a checksum file must be regenerated due to an added checksum type.

This double-free was observed at UCSD when CVMFS checksums were requested for files written prior to the CVMFS-style checksum support.

Further, this release fixes a potential deadlock in the SIGSEGV signal handler due to prior use of async signal unsafe functions.

GridFTP HDFS with "CVMFS" checksums

This release adds some exciting new improvements to the GridFTP checksum code. A new checksum type, CVMFS is added, which provides a checksum per fixed-sized block within the file. As the name suggests, this is precisely the checksum type used internally within CVMFS (see https://cernvm.cern.ch/portal/filesystem), providing an easy mechanism for publishing the contents of a GridFTP server into CVMFS.

Additionally, special thanks goes out to @JasonAlt who provided several useful bugfixes for this release:

• Edge cases around zero-sized files are handled correctly.
• Deadlocks around the separate HDFS log monitor thread are now avoided.
• Additionally, Jason found and fixed a few memory and file permission issues in the CVMFS code prior to its release.

GridFTP HDFS OSG-based Release

This is the first release of the GridFTP-HDFS from the OSG organization:

• All downstream patches the OSG applies have now been applied to the source.
• Merges in the private bbockelm fork.
• Change install of package to modern GridFTP configurations.
• Top-to-bottom replacement of the build system.