Allow disabling PID loops at runtime

<design concept>
Add the map of object enable interface to pid loops
in the zone then we can disable/enable each pid loop
process in a zone by dbus command.

[note]
Enable = true  : enable process (default)
Enable = false : disable process

Tested:
In this case: we set Enable = false to disable
pidloop:Zone_Temp_0, and see how it affects
the zone final pwm, when pidloop: Zone_Temp_0
in zone 0 is disabled.

then even we are trying to heat up the temperature
of a sensor: Temp_0 in pidloop: Zone_Temp_0, this
set point of the pidloop will not be taken into the
calculation for the final set point of the whole zone.

```
<service object>
root@openbmc:/tmp# busctl tree xyz.openbmc_project.State.FanCtrl
`-/xyz
  `-/xyz/openbmc_project
    `-/xyz/openbmc_project/settings
      `-/xyz/openbmc_project/settings/fanctrl
        |-/xyz/openbmc_project/settings/fanctrl/zone0
        | |-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp
        | |-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
        | `-/xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_1

====Enable process for pidloop:Zone_Temp_0 with p-switch temperature sensor:Temp_0 at runtime====
root@openbmc:~# busctl introspect xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
xyz.openbmc_project.Object.Enable   interface -         -            -
.Enabled                            property  b         true         emits-change writable

====Disable process for pidloop:Zone_Temp_0 with p-switch temperature sensor: Temp_0====
root@openbmc:~# busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0 xyz.openbmc_project.Object.Enable Enabled b false
root@openbmc:~# busctl introspect xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0/Zone_Temp_0
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
xyz.openbmc_project.Object.Enable   interface -         -            -
.Enabled                            property  b         false        emits-change writable
```

when Disable the process of the pidloop: Zone_Temp_0,
the requester switches from Zone_Temp_0 to the others,
when you enable the pidloop: Zone_Temp_0, the setpoint
of Zone_Temp_0 will be take into consideration again

Change-Id: I95ae700144f0d16049fff8b309f05ae690a7ef72
Signed-off-by: ykchiu <Chiu.YK@inventec.com>
diff --git a/test/helpers.hpp b/test/helpers.hpp
index 8f81bc6..4d3faea 100644
--- a/test/helpers.hpp
+++ b/test/helpers.hpp
@@ -45,6 +45,7 @@
     EXPECT_CALL(*sdbus_mock,
                 sd_bus_add_object_vtable(IsNull(), NotNull(), StrEq(path),
                                          StrEq(intf), NotNull(), NotNull()))
+        .Times(::testing::AnyNumber())
         .WillOnce(Return(0));
 
     if (!defer)