Do not add line break to the end of stdout/stderr

gsutil.py adds a line break at the end of stdout/stderr when luci-auth is used. This change fixes it.

R=sokcevic, jojwang

Bug: 1412249, 1359383
Change-Id: Ieb200db94d9ed9149e17df93c33802a7433a8d5d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4221262
Auto-Submit: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Joanna Wang <jojwang@chromium.org>
Reviewed-by: Joanna Wang <jojwang@chromium.org>

gsutil.py

@@ -171,10 +171,10 @@ def luci_context(cmd):
     return _run_subprocess(cmd, interactive=True)
 
   if p.stdout:
-    print(p.stdout.decode('utf-8'))
+    print(p.stdout.decode('utf-8'), end='')
 
   if p.stderr:
-    print(p.stderr.decode('utf-8'), file=sys.stderr)
+    print(p.stderr.decode('utf-8'), file=sys.stderr, end='')
 
   return p