ceph-volume: process: write stdin using "Popen.stdin"

we cannot use process.communicate() to feed the Popen with input,
because, upon return of process.communicate() the stdout,stderr are
closed. so, we need to write to Popen.stdin property instead.

Signed-off-by: Kefu Chai <kchai@redhat.com>

src/ceph-volume/ceph_volume/process.py

@@ -114,7 +114,8 @@ def run(command, **kw):
     )
 
     if stdin:
-        process.communicate(stdin)
+        process.stdin.write(stdin)
+        process.stdin.close()
     while True:
         reads, _, _ = select(
             [process.stdout.fileno(), process.stderr.fileno()],