rebase: vendor dependencies for Vault API

Uses github.com/libopenstorage/secrets to communicate with Vault. This
removes the need for maintaining our own limited Vault APIs.

By adding the new dependency, several other packages got updated in the
process. Unused indirect dependencies have been removed from go.mod.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

vendor/golang.org/x/net/http2/http2.go

@@ -241,6 +241,7 @@ func (cw closeWaiter) Wait() {
 // Its buffered writer is lazily allocated as needed, to minimize
 // idle memory usage with many connections.
 type bufferedWriter struct {
+	_  incomparable
 	w  io.Writer     // immutable
 	bw *bufio.Writer // non-nil when data is buffered
 }
@@ -313,6 +314,7 @@ func bodyAllowedForStatus(status int) bool {
 }
 
 type httpError struct {
+	_       incomparable
 	msg     string
 	timeout bool
 }
@@ -376,3 +378,8 @@ func (s *sorter) SortStrings(ss []string) {
 func validPseudoPath(v string) bool {
 	return (len(v) > 0 && v[0] == '/') || v == "*"
 }
+
+// incomparable is a zero-width, non-comparable type. Adding it to a struct
+// makes that struct also non-comparable, and generally doesn't add
+// any size (as long as it's first).
+type incomparable [0]func()