autotest: move default autodir to /usr/local/tmp

We want to remove exec from /tmp on test images, so move the autotest
base install path out of /tmp and into /usr/local/tmp.  There are a
lot of programs under bin/ there that autotest likes to execute.

BUG=chromium:936818
TEST=precq passes

Change-Id: I6ffda45873ed643e5b3d26b2ce3148044868c904
Reviewed-on: https://chromium-review.googlesource.com/1682872
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
diff --git a/server/hosts/remote.py b/server/hosts/remote.py
index ea3ae06..fdad7ac 100644
--- a/server/hosts/remote.py
+++ b/server/hosts/remote.py
@@ -29,7 +29,7 @@
     _DETECTABLE_LABELS = []
 
     VAR_LOG_MESSAGES_COPY_PATH = "/var/tmp/messages.autotest_start"
-    TMP_DIR_TEMPLATE = 'autoserv-XXXXXX'
+    TMP_DIR_TEMPLATE = '/usr/local/tmp/autoserv-XXXXXX'
 
 
     def _initialize(self, hostname, autodir=None, *args, **dargs):