Fix exact tag detection when the commit has several tags
Fix exact tag detection when the commit has several tags

By design, git describe will always pick up the latest tag. Use git tag
"points at" functionality to allow for MENDER_REV to be and old tag
which points to a commit shared by newer tags.

Changelog: None

Signed-off-by: Lluis Campos <9244cb41c39addfc5cf236920b776ea2820513d0@northern.tech>

mendersoftware/meta-mender-qemu