recvfrom01: Fix invalid flags in testcase 4

The recv testcases had reported failures on 3.17-rc. [1]

Three of those failures were invalid assumptions about kernel behavior
with every possible flag set. [2]

The fourth failure is because recfrom01 testcase 4 has invalid message
flags in addition to its invalid address length, making it equivalent
to test 6 (because the flags get checked  first).

Remove the invalid flags, and change the text so it's more clear what
is being tested.

Also fix indentation that made it harder to spot this bug.

Version 2: Add better text and remove an erroneous change to the
buffer length spotted by Jan Stancek.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1145325
[2] http://marc.info/?t=141148149900006&r=1&w=2

Signed-off-by: Chuck Ebbert <cebbert.lkml@gmail.com>
Reviewed-by: Jan Stancek <jstancek@redhat.com>