Bluetooth: Mesh: Do not relay message rejected by Transport layer

Mesh Profile Specification Errata 11341

3.6.4.3 Message error procedure
When the Upper Transport layer receives a message that is not
understood, then the message shall be ignored.
A message that is not understood includes messages that met one or more
conditions listed below:
• The Transport Control message opcode is unknown by the receiving node.
• The Transport Control message size for the Transport Control opcode
is incorrect.
• The Transport Control message parameters contain values that are
Prohibited

Signed-off-by: Michał Narajowski <michal.narajowski@codecoup.pl>