[test] Replaced some if true {} statements with do {} (#2117)

Author: ceyhun

test/Interpreter/SDK/CALayer.swift

@@ -40,7 +40,7 @@ class FooLayer: CALayer {
   }
 }
 
-if true {
+do {
   let layer = FooLayer()
   print("\(layer)")
 }

test/Interpreter/SDK/CoreGraphics_CGFloat.swift

@@ -102,15 +102,15 @@ CGFloatTestSuite.test("arithmetic") {
 }
 
 CGFloatTestSuite.test("striding") {
-  if true {
+  do {
     var result = [CGFloat]()
     for f in stride(from: (1.0 as CGFloat), to: 2.0, by: 0.5) {
       result.append(f)
     }
     expectEqual([ 1.0, 1.5 ], result)
   }
 
-  if true {
+  do {
     var result = [CGFloat]()
     for f in stride(from: (1.0 as CGFloat), through: 2.0, by: 0.5) {
       result.append(f)
@@ -121,7 +121,7 @@ CGFloatTestSuite.test("striding") {
 
 CGFloatTestSuite.test("bridging") {
   // Bridging to NSNumber.
-  if true {
+  do {
     let flt: CGFloat = 4.125
 
     // CGFloat -> NSNumber conversion.
@@ -134,7 +134,7 @@ CGFloatTestSuite.test("bridging") {
   }
 
   // Array bridging.
-  if true {
+  do {
     let originalArray: [CGFloat] = [ 4.125, 10.625 ]
 
     // Array -> NSArray