[buildbot] phase1: also honour branch in Git() step

[LEDE Commits]

jow pushed a commit to buildbot.git, branch master:
https://git.lede-project.org/efbdd4d07b51f7d3de43ebf9198b7d051044bc51

commit efbdd4d07b51f7d3de43ebf9198b7d051044bc51
Author: Jo-Philipp Wich <jo at mein.io>
AuthorDate: Mon Nov 14 15:17:46 2016 +0100

    phase1: also honour branch in Git() step
    
    Signed-off-by: Jo-Philipp Wich <jo at mein.io>
---
 phase1/master.cfg | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/phase1/master.cfg b/phase1/master.cfg
index 91cc1a7..b9fd34e 100644
--- a/phase1/master.cfg
+++ b/phase1/master.cfg
@@ -264,7 +264,7 @@ for target in targets:
 		))
 
 	# check out the source
-	factory.addStep(Git(repourl=repo_url, mode='update'))
+	factory.addStep(Git(repourl=repo_url, branch=repo_branch, mode='update'))
 
 	factory.addStep(ShellCommand(
 		name = "rmtmp",