If start_server() fails, then pid will end up with -1 and
cleanup() will do kill(-1, SIGKILL), which kills everything
this process can kill.

Change the test to kill pid (child) only when it successfully
creates one.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
  testcases/kernel/syscalls/recvmsg/recvmsg01.c |    5 +++--
  1 files changed, 3 insertions(+), 2 deletions(-)