automation: fix sed expression
automation: fix sed expression

make distcheck performs tests within extracted tarball
so we are using sed to remove the heading dist directory.
Fixed the expression for making master suffix optional.

Change-Id: I4b5fd5a635f632bc93494d9f88c8afcbc0ac2152
Signed-off-by: Sandro Bonazzola <fcb014d63786651910af5db2ecc5316c668188ef@redhat.com>

oVirt/ovirt-setup-lib,oVirt/ovirt-setup-lib,oVirt/ovirt-setup-lib,oVirt/ovirt-setup-lib