[nrf fromtree] tests: bluetooth: tester: mesh: Increase CMD tx bufs

Increase CONFIG_BT_BUF_CMD_TX_COUNT to avoid deadlock when running out
of buffers. See #77241 for the reference.

This fixes Mesh Provisioning Service tests (MESH/NODE/MPS).

Signed-off-by: Pavel Vasilyev <[email protected]>
(cherry picked from commit 6c35d37)

Author: PavelVPV

tests/bluetooth/tester/overlay-mesh.conf

@@ -58,3 +58,6 @@ CONFIG_BT_MESH_COMP_PAGE_2=y
 CONFIG_BT_MESH_BRG_CFG_SRV=y
 CONFIG_BT_MESH_BRG_CFG_CLI=y
 CONFIG_SETTINGS=y
+
+# Increase the number of buffers to avoid deadlock when running out of buffers
+CONFIG_BT_BUF_CMD_TX_COUNT=4