qmp-shell: learn to send commands with quoted arguments

Use shlex to split the CLI command, respecting quoted arguments, and
also comments. This allows to call for ex:

(QEMU) human-monitor-command command-line="screendump /dev/null"
{"execute": "human-monitor-command", "arguments": {"command-line": "screendump /dev/null"}}
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180326150916.9602-3-marcandre.lureau@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

scripts/qmp/qmp-shell

@@ -74,6 +74,7 @@ import sys
 import os
 import errno
 import atexit
+import shlex
 
 class QMPCompleter(list):
     def complete(self, text, state):
@@ -219,7 +220,7 @@ class QMPShell(qmp.QEMUMonitorProtocol):
 
             < command-name > [ arg-name1=arg1 ] ... [ arg-nameN=argN ]
         """
-        cmdargs = cmdline.split()
+        cmdargs = shlex.split(cmdline)
 
         # Transactional CLI entry/exit:
         if cmdargs[0] == 'transaction(':