Revert "[Fuchsia] Update test runner to use /tmp for output minfs image."

This reverts commit d6a88b16c1c35715a0dfba78e5878b8a77c48dd7.

Reason for revert: net_unittests still fails.

Original change's description:
> [Fuchsia] Update test runner to use /tmp for output minfs image.
> 
> /tmp is expected to perform better on GCE when used as a backing
> storage for minfs disk image, which should make fsync() less
> likely to timeout when writing output.json.
> 
> Bug: 796318
> Change-Id: I6a410d9b7284623ad5ad490225e4f489395a881d
> Reviewed-on: https://chromium-review.googlesource.com/838511
> Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
> Reviewed-by: Wez <wez@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#525784}

TBR=wez@chromium.org,sergeyu@chromium.org

Change-Id: Ieb709b65af577712862b8538d3e33a2f8aed81ee
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 796318
Reviewed-on: https://chromium-review.googlesource.com/841242
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#525816}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 11400a4b68ae249b919ba918d9d302ff463c9c63

fuchsia/runner_common.py

@@ -17,7 +17,6 @@ import signal
 import subprocess
 import sys
 import tarfile
-import tempfile
 import time
 import uuid
 
@@ -533,13 +532,12 @@ def _SymbolizeBacktrace(backtrace, symbols_mapping):
   return map(lambda entry: symbolized[entry['frame_id']], backtrace)
 
 
-def _GetResultsFromImg(dry_run, disk_image_filename,
-                       test_launcher_summary_output):
+def _GetResultsFromImg(dry_run, test_launcher_summary_output):
   """Extract the results .json out of the .minfs image."""
   if os.path.exists(test_launcher_summary_output):
     os.unlink(test_launcher_summary_output)
-  _RunAndCheck(dry_run, [os.path.join(SDK_ROOT, 'tools', 'minfs'),
-                         disk_image_filename,
+  img_filename = test_launcher_summary_output + '.minfs'
+  _RunAndCheck(dry_run, [os.path.join(SDK_ROOT, 'tools', 'minfs'), img_filename,
                          'cp', '::/output.json', test_launcher_summary_output])
 
 
@@ -688,15 +686,13 @@ def RunFuchsia(bootfs_data, use_device, kernel_path, dry_run,
     if test_launcher_summary_output:
       # Make and mount a 100M minfs formatted image that is used to copy the
       # results json to, for extraction from the target.
-      summary_disk_image = tempfile.NamedTemporaryFile(
-          prefix="output.json.minfs")
-      _RunAndCheck(dry_run, ['truncate', '-s100M',
-                             summary_disk_image.name,])
+      img_filename = test_launcher_summary_output + '.minfs'
+      _RunAndCheck(dry_run, ['truncate', '-s100M', img_filename,])
       _RunAndCheck(dry_run, [os.path.join(SDK_ROOT, 'tools', 'minfs'),
-                             summary_disk_image.name, 'mkfs'])
+                             img_filename, 'mkfs'])
       # Specifically set an AHCI drive, otherwise the drive won't be mountable
       # on ARM64.
-      qemu_command.extend(['-drive', 'file=' + summary_disk_image.name +
+      qemu_command.extend(['-drive', 'file=' + img_filename +
                                ',if=none,format=raw,id=resultsdisk',
                            '-device', 'ahci,id=ahci',
                            '-device', 'ide-drive,drive=resultsdisk,bus=ahci.0'])
@@ -722,7 +718,6 @@ def RunFuchsia(bootfs_data, use_device, kernel_path, dry_run,
   sys.stdout.flush()
 
   if test_launcher_summary_output:
-    _GetResultsFromImg(dry_run, summary_disk_image.name,
-                       test_launcher_summary_output)
+    _GetResultsFromImg(dry_run, test_launcher_summary_output)
 
   return 0 if success else 1