Documentation has broken paths

[crawford]

There are a number of broken links in the docs, as detected by marker:

Found absolute path    (benchmark hacking guide -> /hack/benchmark/) at ./Documentation/benchmarks/etcd-2-1-0-alpha-benchmarks.md:17
Found absolute path    (benchmark hacking guide -> /hack/benchmark/) at ./Documentation/benchmarks/etcd-2-2-0-rc-benchmarks.md:27
Found absolute path    (etcd v3 benchmark tool -> /tools/benchmark/) at ./Documentation/benchmarks/etcd-3-demo-benchmarks.md:17
Found broken path      (capnslog -> [https://github.com/coreos/pkg/tree/master/capnslog]) at ./Documentation/dev-internal/logging.md:3
Found absolute path    (TLS setup -> /hack/tls-setup) at ./Documentation/op-guide/clustering.md:81
Found absolute path    (here -> /hack/tls-setup) at ./Documentation/op-guide/security.md:7
Found absolute path    (benchmark hacking guide -> /hack/benchmark/) at ./Documentation/v2/benchmarks/etcd-2-1-0-alpha-benchmarks.md:17
Found broken path      (benchmark instructions -> ../../hack/benchmark/) at ./Documentation/v2/benchmarks/etcd-2-2-0-benchmarks.md:27
Found absolute path    (benchmark hacking guide -> /hack/benchmark/) at ./Documentation/v2/benchmarks/etcd-2-2-0-rc-benchmarks.md:27
Found absolute path    (etcd v3 benchmark tool -> /tools/benchmark/) at ./Documentation/v2/benchmarks/etcd-3-demo-benchmarks.md:17
Found broken path      (Procfile script -> ./Procfile) at ./Documentation/v2/README.md:76
Found broken path      (LICENSE -> LICENSE) at ./Documentation/v2/README.md:165
Found broken path      (persistent -> [https://en.wikipedia.org/wiki/Persistent_data_structure]) at ./Documentation/v2/api_v3.md:9
Found broken path      (b+tree -> [https://en.wikipedia.org/wiki/B%2B_tree]) at ./Documentation/v2/api_v3.md:21
Found broken path      (btree -> [https://en.wikipedia.org/wiki/B-tree]) at ./Documentation/v2/api_v3.md:25
Found broken path      (sequential consistency -> [https://en.wikipedia.org/wiki/Consistency_model#Sequential_consistency]) at ./Documentation/v2/api_v3.md:60
Found broken path      (linearized -> [#Linearizability]) at ./Documentation/v2/api_v3.md:62
Found broken path      (strict consistency -> [https://en.wikipedia.org/wiki/Consistency_model#Strict_consistency]) at ./Documentation/v2/api_v3.md:64
Found broken path      (serializable isolation -> [https://en.wikipedia.org/wiki/Isolation_(database_systems)#Serializable]) at ./Documentation/v2/api_v3.md:68
Found absolute path    (etcd/client -> /client) at ./Documentation/v2/clustering.md:399
Found absolute path    (here -> /hack/tls-setup) at ./Documentation/v2/security.md:7

The following two commits (in the master branch) correct the absolute paths. Please backport them to the next releases.

31c1931
e0de653

The other broken links still exist in the master branch.

[gyuho]

Ok, will backport those two commits to release-3.1 branch.

Thanks!