Enable and use salt_api proxy by default

 * Use nginx as proxy
 * Misc: define defaults for
    salt_master_host
    infra_config_address
    reclass_config_master
    jenkins_salt_api_url
 * Pass certs dir for jenkins docker slaves

Related: PROD-27641(PROD:27641)
Related: PROD-30528(PROD:30528)

Change-Id: I5fac90101131a8d8d4fa7857982f18c855e0771c
diff --git a/defaults/salt/init.yml b/defaults/salt/init.yml
index a720189..0b80c35 100644
--- a/defaults/salt/init.yml
+++ b/defaults/salt/init.yml
@@ -57,3 +57,4 @@
     - '@jobs'    # to allow access to the jobs runner and/or wheel mo
 
     salt_minion_ca_authority: salt_master_ca
+    salt_master_api_bind_address: 0.0.0.0