Bump aws sdk to v1.15.11

This is the latest official release for this dependency

Signed-off-by: Ryan Abrams <rdabrams@gmail.com>

vendor/github.com/aws/aws-sdk-go/internal/sdkio/io_go1.6.go

@@ -0,0 +1,10 @@
+// +build !go1.7
+
+package sdkio
+
+// Copy of Go 1.7 io package's Seeker constants.
+const (
+	SeekStart   = 0 // seek relative to the origin of the file
+	SeekCurrent = 1 // seek relative to the current offset
+	SeekEnd     = 2 // seek relative to the end
+)

vendor/github.com/aws/aws-sdk-go/internal/sdkio/io_go1.7.go

@@ -0,0 +1,12 @@
+// +build go1.7
+
+package sdkio
+
+import "io"
+
+// Alias for Go 1.7 io package Seeker constants
+const (
+	SeekStart   = io.SeekStart   // seek relative to the origin of the file
+	SeekCurrent = io.SeekCurrent // seek relative to the current offset
+	SeekEnd     = io.SeekEnd     // seek relative to the end
+)

vendor/github.com/aws/aws-sdk-go/internal/sdkrand/locked_source.go

@@ -0,0 +1,29 @@
+package sdkrand
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// lockedSource is a thread-safe implementation of rand.Source
+type lockedSource struct {
+	lk  sync.Mutex
+	src rand.Source
+}
+
+func (r *lockedSource) Int63() (n int64) {
+	r.lk.Lock()
+	n = r.src.Int63()
+	r.lk.Unlock()
+	return
+}
+
+func (r *lockedSource) Seed(seed int64) {
+	r.lk.Lock()
+	r.src.Seed(seed)
+	r.lk.Unlock()
+}
+
+// SeededRand is a new RNG using a thread safe implementation of rand.Source
+var SeededRand = rand.New(&lockedSource{src: rand.NewSource(time.Now().UnixNano())})

vendor/github.com/aws/aws-sdk-go/internal/sdkuri/path.go

@@ -0,0 +1,23 @@
+package sdkuri
+
+import (
+	"path"
+	"strings"
+)
+
+// PathJoin will join the elements of the path delimited by the "/"
+// character. Similar to path.Join with the exception the trailing "/"
+// character is preserved if present.
+func PathJoin(elems ...string) string {
+	if len(elems) == 0 {
+		return ""
+	}
+
+	hasTrailing := strings.HasSuffix(elems[len(elems)-1], "/")
+	str := path.Join(elems...)
+	if hasTrailing && str != "/" {
+		str += "/"
+	}
+
+	return str
+}