Channel switching issue in MAC layer occurs when there is no NW forma…

…tion (openthread#9394)

- This commit resolves inconsistency between Host and RCP channel on scan
energy when network not created.
- Added fix in MAC layer to update the channel on scan energy

src/core/mac/mac.cpp

@@ -340,6 +340,10 @@ void Mac::PerformEnergyScan(void)
  }
  else
  {
+ if(!GetRxOnWhenIdle())
+ {
+ SuccessOrAssert(Get().Receive(mScanChannel));
+ }
  error = mLinks.EnergyScan(mScanChannel, mScanDuration);
  }