Fix processing of files with an XZ compressed control file

[mpoindexter]

Fixes a bug uploading deb packages when the control file is compressed using XZ.

• Fixes 500 Error when Uploading Ubuntu Kernel Packages #52

This pull request makes the following changes:

• Adds a break statement in the switch to detect control file type
• Changes the decompressor for GZ control files to use the one from commons-compress instead of the JDK. Might fix Error when using S3 blobstore: java.io.IOException: failed to read entry trailer. Occured at byte: 46324 #43, based on some reports on the internet but I don't have a S3 bucket to test this out on.

[brianpatrickreavey]

I do not believe this fixed #43. I get the same error on OSS 3.13.0-01, and the most recent apt repository plugin.

Any attempts to upload a .deb to an apt repo with the S3-blob backend fails with an error:

java.io.IOException: failed to read entry trailer. Occured at byte: <size of file>

Using the default blob store works fine. This occurs via the UI, or curl.