systemd: add knot-resolver alias

The `knot-resolver` name is used for paths and user name. Creating a
systemd alias with the same name is user-friendly to end users who won't
have to remember another name (`kresd`).

Note: Systemd Alias is only created after service is enabled. Packagers
are thus advised to create symlinks for unit files during package installation
so users can use `knot-resolver` name right from the start.
12 jobs for systemd-modifications in 6 minutes and 42 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Build
passed #96985
docker linux amd64
build:linux:amd64

00:00:26

 
  Test
passed #96990
docker linux amd64
deckard:linux:amd64

00:06:01

passed #96989
docker linux amd64
installcheck:linux:amd64

00:00:27

passed #96991
docker linux amd64
installcheck:valgrind:linux:amd64

00:00:39

failed #96987
docker allowed to fail
lint:clang-scan-build

00:00:40

passed #96986
docker
lint:lua

00:00:19

passed #96994
docker linux amd64
respdiff:iter:tcp:linux:amd64

00:01:58

passed #96995
docker linux amd64
respdiff:iter:tls:linux:amd64

00:02:07

passed #96993
docker linux amd64
respdiff:iter:udp:linux:amd64

00:02:09

passed #96988
docker linux amd64
test:linux:amd64

00:00:36

passed #96992
docker linux amd64
test:linux:amd64:valgrind

00:00:35

 
  Coverage
passed #96996
docker linux amd64
coverage

00:00:12

65.6%
 
Name Stage Failure
failed
lint:clang-scan-build Test There is an unknown failure, please try again
                        ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
CCLD daemon/kresd
scan-build: 40 bugs found.
scan-build: Run 'scan-view /builds/knot/knot-resolver/scan-results/2018-01-11-182044-13-1' to examine bug reports.
Uploading artifacts...
scan-results: found 45 matching files
Uploading artifacts to coordinator... ok
id=96987 responseStatus=201 Created token=nNfZD9Xu
ERROR: Job failed: exit code 1