Fix clearing new session ticket message

[Ryanfsdf]

Fixed the issue of not clearing the body of the message when receiving a new session ticket. This caused issues when communication with a Go/C++ greeter server.

Also, I changed the code to clear the entire p.pendingApplicationData. Before, we didn't clear the entire buffer in case there were trailing bytes that we were still interested in. However, for handshake messages and alerts, I don't think there will ever be trailing bytes at the end.

---

This change is 

[matthewstevenson88]

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @matthewstevenson88 and @Ryanfsdf)

---

security/s2a/internal/record/record_test.go, line 1079 at r2 (raw file):

				t.Fatalf("c.Read(plaintext) failed: %v", err)
			}
			if got, want := len(c.(*conn).pendingApplicationData), 0; got != want {

Should we also check that plaintext consists of all zeros? I.e. no application data was written?

[Ryanfsdf]

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @matthewstevenson88)

---

security/s2a/internal/record/record_test.go, line 1079 at r2 (raw file):

Previously, matthewstevenson88 wrote…

Should we also check that plaintext consists of all zeros? I.e. no application data was written?

Done.

[matthewstevenson88]

Reviewable status: 0 of 2 files reviewed, all discussions resolved