fix broken links

Signed-off-by: Fedor Partanskiy <fredprtnsk@gmail.com>

Author: pfi79

docs/source/glossary.rst

@@ -547,7 +547,7 @@ Raft
 ----
 
 New for v1.4.1, Raft is a crash fault tolerant (CFT) ordering service
-implementation based on the `etcd library <https://coreos.com/etcd/>`_
+implementation based on the `etcd library <https://etcd.io/>`_
 of the `Raft protocol <https://raft.github.io/raft.pdf>`_. Raft follows a
 "leader and follower" model, where a leader node is elected (per channel) and
 its decisions are replicated by the followers.

docs/source/orderer/ordering_service.md

@@ -189,7 +189,7 @@ implementation the node will be used in), check out [our documentation on deploy
 
   New as of v1.4.1, Raft is a crash fault tolerant (CFT) ordering service
   based on an implementation of [Raft protocol](https://raft.github.io/raft.pdf)
-  in [`etcd`](https://coreos.com/etcd/). Raft follows a "leader and
+  in [`etcd`](https://etcd.io/). Raft follows a "leader and
   follower" model, where a leader node is elected (per channel) and its decisions
   are replicated by the followers.
 

docs/source/whatis.md

@@ -179,7 +179,7 @@ The order-execute architecture can be found in virtually all existing blockchain
 systems, ranging from public/permissionless platforms such as
 [Ethereum](https://ethereum.org/) (with PoS-based consensus) to permissioned
 platforms such as [Tendermint](http://tendermint.com/),
-[Chain](http://chain.com/), and [Quorum](https://docs.goquorum.consensys.io/).
+[Chain](http://chain.com/), and [Quorum](https://goquorum.readthedocs.io/).
 
 Smart contracts executing in a blockchain that operates with the order-execute
 architecture must be deterministic; otherwise, consensus might never be reached.