test: revert changes made for Go SSA interpreter test.

R=r, gri
CC=golang-dev
https://golang.org/cl/14552044

test/blank.go

@@ -111,8 +111,7 @@ func main() {
 		panic(sum)
 	}
 
-	// exp/ssa/interp doesn't yet skip blank fields in struct
-	// equivalence.  It also cannot support unsafe.Pointer.
+	// go.tools/ssa/interp cannot support unsafe.Pointer.
 	if os.Getenv("GOSSAINTERP") == "" {
 		type T1 struct{ x, y, z int }
 		t1 := *(*T)(unsafe.Pointer(&T1{1, 2, 3}))

test/nilptr2.go

@@ -6,8 +6,6 @@
 
 package main
 
-import "os"
-
 func main() {
 	ok := true
 	for _, tt := range tests {
@@ -23,7 +21,6 @@ func main() {
 	}
 	if !ok {
 		println("BUG")
-		os.Exit(1)
 	}
 }