Fix corruption via buffer overflow in mediaserver

change unbound sprintf() to snprintf() so network-provided values
can't overflow the buffers.

Applicable to all K/L/M/N branches.

Bug: 25747670
Change-Id: Id6a5120c2d08a6fbbd47deffb680ecf82015f4f6

bool ASessionDescription::isValid() const {
 return mIsValid;
}

bool ASessionDescription::isValid() const {
 return mIsValid;
}
