Dockerfiles: don't ignore make failures

Commit 299e4b4 ("travis: enable ccache for docker/qemu builds") combined
multiple RUN statements in Dockerfiles into a single one, which is good
for performance (as there is an intermediate cache created after each
statement). Unfortunately, it partially did so by combining statements
with use of semicolons, meaning we are ignoring non-zero exit codes.
As a result, failure from make are ignored and Travis builds are all
green.

To fix, replace all occurences of semicolon with &&.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>