debian: Add Jenkins BUILD_NUMBER to package version

For builds triggered by Jenkins on unstable code add number of Jenkins'
build to package version, e.g. 2.5.5.205 -- build #205, LizardFS version
2.5.5. This makes it possible to install these packages using apt-get
upgrade. Additionally put information about refspec of the packaged
commit and its SHA1 hash.

This change doesn't influence builds triggered with an option
OFFICIAL_RELEASE=true. In such a case changelog isn't modified.

Change-Id: Ib86f9bfe02a909410250c672a10f26f2f13779cd