Unsuccessful unlocking of QNetworkConfigurationPrivate mutex

Unsuccessful unlocking of QNetworkConfigurationPrivate mutex

Above mentioned mutex is locked twice: first in caller function and second time in called function. Called function unlocks mutex and emits signal clearly unaware that the mutex is actually still locked. I changed the mutex to be unlocked before the function is called.

Task-number: QTBUG-15108
Reviewed-by: Ville Pernu
(cherry picked from commit c15560fbe2a1762117395c5ecaaecfa5ab8dce6f)