mod_turncredentials: Add 'transport' attribute XEP-0215 recommends using 'transport' attribute and since coturn can work in both TCP and UPD modes this patch adds one <service> element for each combination of STUN/TURN and TCP/UDP.

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summary: Allow server administrators to probe any user
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This module lets server administrators send `<presence type="probe"/>`
to any local user and receive their presence in response, bypassing
roster checks.