only emit a single space between mac length and the orginal id if the mac length is zero

(cherry picked from commit ac1c3aaa)
14 jobs for 540-tsig-has-two-consecutive-spaces-when-maclen-is-0-v9_12 in 7 minutes and 47 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #59230
amd64 docker linux

00:00:19

 
  Build
passed build:centos:centos6:amd64 #59231
amd64 docker linux

00:02:14

passed build:centos:centos7:amd64 #59232
amd64 docker linux

00:02:23

passed build:debian:sid:amd64 #59233
amd64 docker linux

00:01:24

passed build:debian:sid:i386 #59234
i386 docker linux

00:01:48

 
  Test
passed install:debian:sid:amd64 #59243
amd64 docker linux

00:02:58

passed systemtest:centos:centos6:amd64 #59239
amd64 docker linux

00:04:49

passed systemtest:centos:centos7:amd64 #59240
amd64 docker linux

00:04:46

passed systemtest:debian:sid:amd64 #59241
amd64 docker linux

00:04:57

passed systemtest:debian:sid:i386 #59242
i386 docker linux

00:05:02

passed unittest:centos:centos6:amd64 #59235
amd64 docker linux

00:01:10

passed unittest:centos:centos7:amd64 #59236
amd64 docker linux

00:01:12

passed unittest:debian:sid:amd64 #59237
amd64 docker linux

00:01:02

passed unittest:debian:sid:i386 #59238
i386 docker linux

00:01:01