buildbot: exit 0 at the end of the script

This permits script to return correct state when skipping packaging
23 jobs for master in 25 minutes and 57 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build
passed #18281642
build:debian-8

00:18:59

passed #18281643
build:debian-9

00:09:54

passed #18281648
build:fedora-24

00:12:04

passed #18281644
build:ubuntu-14.04

00:12:27

passed #18281645
build:ubuntu-16.04

00:12:58

passed #18281646
build:ubuntu-16.10

00:14:55

passed #18281647
build:ubuntu-17.04

00:10:13

passed #18281649
build:win32

00:08:22

passed #18281650
build:win64

00:08:35

 
  Package
passed #18281651
package:debian-8

00:05:21

passed #18281652
package:debian-9

00:01:51

passed #18281653
package:ubuntu-14.04

00:05:12

passed #18281654
package:ubuntu-16.04

00:02:27

passed #18281655
package:ubuntu-16.10

00:05:01

passed #18281656
package:ubuntu-17.04

00:01:57

passed #18281657
package:win32

00:01:59

passed #18281658
package:win64

00:02:48

 
  Deploy
passed #18281659
deploy:debian-8

00:01:28

passed #18281660
deploy:debian-9

00:01:20

passed #18281661
deploy:ubuntu-14.04

00:01:23

passed #18281662
deploy:ubuntu-16.04

00:01:15

passed #18281663
deploy:ubuntu-16.10

00:01:26

passed #18281664
deploy:ubuntu-17.04

00:01:28