CSIT-844: fix binary api rx pthread heap push/pop

CSIT-844: fix binary api rx pthread heap push/pop

We need to push/pop the rx pthread's heap without affecting other
thread(s).

Search clib_per_cpu_mheaps, locate an unused slot. Duplicate the main
thread heap pointer in that slot, and set __os_thread_index
appropriately.

Don't bail out of vpp_api_test with results pending, e.g. at the end
of a vpp_api_test script. Even though vpp will eventuallly
garbage-collect them, We don't want to leave allocated reply messages
lurking in the api message allocation rings...

This patch is a manual cherry-pick from gerrit 8862

Change-Id: If3c84abe61496905432bfa36767068bad4bd243b
Signed-off-by: Dave Barach <[email protected]>