Misc: make example in travis-ci and fix return value of `ff_connect`.

.travis.yml

@@ -18,3 +18,4 @@ script:
   - make -C dpdk install T=x86_64-native-linuxapp-gcc
   - make -C lib CONF_CFLAGS="-Wno-unused-but-set-variable"
   - make -C tools
+  - make -C example

lib/ff_syscall_wrapper.c

@@ -790,7 +790,7 @@ ff_connect(int s, const struct linux_sockaddr *name, socklen_t namelen)
 
     if ((rc = kern_connectat(curthread, AT_FDCWD, s, &bsdaddr)))
         goto kern_fail;
-    rc = curthread->td_retval[0];
+
     return (rc);
 kern_fail:
     ff_os_errno(rc);