net: ipc_router: Fix reading invalid txn_Ids response return code

In some cases the kernel qmi clients get the response after the
synchronous request timedout. Such response messages will not have valid
transaction Ids. Reading response messages that do not have matching
request transactions should not return the error code to qmi clients.

Ignore the response messages with invalid transaction Ids and return
zero instead of error code to the client.

CRs-Fixed: 730758
Change-Id: I70e5b53b9d4fc9abcabc24f0dc8b6460d2b5d1ee
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>