remove extra exchangeContext cleanup (#6334)
remove extra exchangeContext cleanup (#6334)

Summary of Changes:
-- Reset would do exchange cleanup, remove extra ClearExistingExchangeContext
nestlabs/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip