internal/poll: Avoid evaluating condition for an unreachable branch

Change-Id: I868dcaf84767d631bc8f1b6ef6bcb3ec18047259
Reviewed-on: https://go-review.googlesource.com/116135Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/internal/poll/sendfile_bsd.go

@@ -32,8 +32,7 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
 			pos += int64(n)
 			written += int64(n)
 			remain -= int64(n)
-		}
-		if n == 0 && err1 == nil {
+		} else if n == 0 && err1 == nil {
 			break
 		}
 		if err1 == syscall.EAGAIN {

src/internal/poll/sendfile_linux.go

@@ -29,8 +29,7 @@ func SendFile(dstFD *FD, src int, remain int64) (int64, error) {
 		if n > 0 {
 			written += int64(n)
 			remain -= int64(n)
-		}
-		if n == 0 && err1 == nil {
+		} else if n == 0 && err1 == nil {
 			break
 		}
 		if err1 == syscall.EAGAIN {

src/internal/poll/sendfile_solaris.go

@@ -39,8 +39,7 @@ func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
 			pos += int64(n)
 			written += int64(n)
 			remain -= int64(n)
-		}
-		if n == 0 && err1 == nil {
+		} else if n == 0 && err1 == nil {
 			break
 		}
 		if err1 == syscall.EAGAIN {