go: include vendored modules

RHEL requires the source code for dependencies to be included in the
srpm. The spec file already expects that, but we've only included the
vendored modules (i.e., the `vendor` directory) in the `rhel-8.2.`
branch. Move vendoring to master, so that we can build RHEL packages
from it as well.

This commit is the result of running `go mod vendor`, which includes the
vendored sources and updates go.mod and go.sum files.

Fedora requires the opposite: dependencies should not be vendored. The
spec file already ignores the `vendor` directory by default.

vendor/github.com/google/uuid/README.md

@@ -0,0 +1,19 @@
+# uuid ![build status](https://travis-ci.org/google/uuid.svg?branch=master)
+The uuid package generates and inspects UUIDs based on
+[RFC 4122](http://tools.ietf.org/html/rfc4122)
+and DCE 1.1: Authentication and Security Services. 
+
+This package is based on the github.com/pborman/uuid package (previously named
+code.google.com/p/go-uuid).  It differs from these earlier packages in that
+a UUID is a 16 byte array rather than a byte slice.  One loss due to this
+change is the ability to represent an invalid UUID (vs a NIL UUID).
+
+###### Install
+`go get github.com/google/uuid`
+
+###### Documentation 
+[![GoDoc](https://godoc.org/github.com/google/uuid?status.svg)](http://godoc.org/github.com/google/uuid)
+
+Full `go doc` style documentation for the package can be viewed online without
+installing this package by using the GoDoc site here: 
+http://godoc.org/github.com/google/uuid