qmp: fix handling of boolean values in qmp-shell

qmp-shell converts only integer arguments and the rest
is assumed to be strings which are faithfully sent as
quoted strings by json. But QEMU refuses to accept qmp
command with boolean argument whose value is escaped
as string.

Fix it by special-casing true/false keywords and store
value as corresponding boolean.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

QMP/qmp-shell

@@ -101,7 +101,12 @@ class QMPShell(qmp.QEMUMonitorProtocol):
             try:
                 value = int(opt[1])
             except ValueError:
-                value = opt[1]
+                if opt[1] == 'true':
+                    value = True
+                elif opt[1] == 'false':
+                    value = False
+                else:
+                    value = opt[1]
             qmpcmd['arguments'][opt[0]] = value
         return qmpcmd