Drop some unnecessary lsb_release calls

Since Ib4b05eb7191dd50d25799a0bac51fd15c01b74cb, it's possible to know
the Operating System name with the $DISTRO_NAME environment variable.

This patch makes use of this variable when it's possible.

Change-Id: I3252fb60c8bfcc2859ea4b5b138f5888638aaf3c
Merge "Drop some unnecessary lsb_release calls"