Remove unneed devstack early log file

In the run devstack role we specify a path to devstack_early_log then
hand it to stack.sh as a parameter which stack.sh does nothing with.
While looking at a fix for this it was pointed out that these early logs
make it into the job's output log now so we don't need a special file
for them. Rather than handle this as a special case just let the
job-output.txt log file pick up the logs for us which allows us to
remove this unneeded feature.

Change-Id: I9bedbe91c60257d94173b1c70676dd6c2b49dc91

roles/run-devstack/README.rst

@@ -6,9 +6,3 @@ Run devstack
    :default: /opt/stack
 
    The devstack base directory.
-
-.. zuul:rolevar:: devstack_early_log
-   :default: /opt/stack/log/devstack-early.txt
-
-   The full devstack log that includes the whatever stack.sh logs before
-   the LOGFILE variable in local.conf is honoured.

roles/run-devstack/defaults/main.yaml

@@ -1,2 +1 @@
 devstack_base_dir: /opt/stack
-devstack_early_log: /opt/stack/logs/devstack-early.txt

roles/run-devstack/tasks/main.yaml

@@ -1,5 +1,5 @@
 - name: Run devstack
-  shell: ./stack.sh 2>&1 {{ devstack_early_log }}
+  shell: ./stack.sh 2>&1
   args:
     chdir: "{{devstack_base_dir}}/devstack"
   become: true