DNS-SD pairing hint field is incorrect when using BCM and already commissioned

[chrisdecenzo]

Problem

• The pairing hint field must have bit 2 set (see admin UX) when a device has been commissioned before
• Currently, bit 2 is set only when the device is put into commissioning mode using ECM. When using BCM, bit 2 is not set.

Proposed Solution

Bug is in Dnssd.cpp, method DnssdServer::Advertise, approximate line 379, the following check:

if (mode != chip::Dnssd::CommissioningMode::kEnabledEnhanced)

The fix would be to check if CommissioningMode::kEnabledEnhanced or if CommissioningMode::kEnabledBasic when already commissioned.