Fix autest.sh.in to preserve autest exit code (#12732)

The trailing if-blocks for restoring UDS test directories were
overwriting autest's exit code with 0, causing test failures to
be silently ignored in CI. Now we capture the exit code immediately
after autest runs and exit with it at the end of the script.

Author: bryancall

tests/autest.sh.in

@@ -29,6 +29,7 @@ ${RUNPIPENV} run env autest \
   --build-root ${CMAKE_BINARY_DIR} \
   ${CURL_UDS_FLAG} ${AUTEST_OPTIONS} \
   "$@"
+autest_exit=$?
 
 # Restore tests back to source tree and remove temp dir
 if [ -n "${CURL_UDS_FLAG}" ]; then
@@ -45,3 +46,5 @@ if [ -n "${CURL_UDS_FLAG}" ]; then
     rm -rf "${CMAKE_SKIP_GOLD_DIR}"
   fi
 fi
+
+exit $autest_exit