mdns_search_once_t::lock is used to synchronize tasks (taken by one
task and given by the other) so it should not be a mutex.
Convert to semaphore, and rename to indicate its purpose.
* Original commit: espressif/esp-idf@eef0b5090a
Allocation was happening later, causing possible use of stack variables
of caller function, which could be invalid.
Signed-off-by: Piyush Shah <piyush@espressif.com>
* Original commit: espressif/esp-idf@e5e2702ca3
