vendor: update vendored packages

[ericchiang]

Spring cleaning. Update all of the following packages to pull in latest code:

• github.com/beevik/etree (dep of SAML)
• github.com/coreos/etcd
• github.com/coreos/go-oidc
• github.com/ghodss/yaml
• github.com/go-sql-driver/mysql (maybe remove this?)
• github.com/golang/protobuf (*: fix proto build #1140)
• github.com/gorilla/context
• github.com/gorilla/handlers
• github.com/gorilla/mux
• github.com/gtank/cryptopasta (maybe remove and just copy + paste code)
• github.com/inconshreveable/mousetrap (windows dep of cobra)
• github.com/jonboulle/clockwork (dep of SAML)
• github.com/kylelemons/godebug (test dep)
• github.com/lib/pq
• github.com/mattn/go-sqlite3
• github.com/pquerna/cachecontrol (dep of go-oidc)
• github.com/russellhaering/goxmldsig
• github.com/sirupsen/logrus
• github.com/spf13/cobra
• github.com/spf13/pflag
• golang.org/x/crypto (for bcrypt)
• golang.org/x/net
• golang.org/x/oauth2
• golang.org/x/sys
• golang.org/x/text
• google.golang.org/appengine (dep of oauth2)
• google.golang.org/genproto (dep of grpc)
• google.golang.org/grpc
• gopkg.in/asn1-ber.v1
• gopkg.in/ldap.v2
• gopkg.in/square/go-jose.v2
• gopkg.in/yaml.v2

[sks]

@ericchiang : Are you okay with deleting the vendor directory and moving to go modules ?

[ericchiang]

@sks I'd like to continue to commit vendor. even when we use go modules This helps us when repos get deleted from github.

[fishioon]

@ericchiang The vendored oauth2 not support custom param.
So is time to update vendored packages. 😄

[srenatus]

#1501 ✔️ should be resolved