Raise orchestration build_timeout to 600 seconds

Observed boot time for a single server has been around 250 seconds
so a build_timeout default of 300 would explain why ~20% of heat-slow
jobs are failing with stack timeout errors.

Closes-Bug: #1288970
Change-Id: I4feb1b89acf8db0e164468d0471aff71ff5c6a77
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index ee2da40..bab2471 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -679,7 +679,7 @@
 
 # Timeout in seconds to wait for a stack to build. (integer
 # value)
-#build_timeout=300
+#build_timeout=600
 
 # Instance type for tests. Needs to be big enough for a full
 # OS plus the test workload (string value)
diff --git a/tempest/config.py b/tempest/config.py
index 0f5e23c..d7d8079 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -522,7 +522,7 @@
                default=1,
                help="Time in seconds between build status checks."),
     cfg.IntOpt('build_timeout',
-               default=300,
+               default=600,
                help="Timeout in seconds to wait for a stack to build."),
     cfg.StrOpt('instance_type',
                default='m1.micro',