Improve TC etcd heartbeat keyname and value [#74964832]

Signed-off-by: John Tuley <jtuley@pivotallabs.com>
add LoggregatorClientPool

[#74964832]

Signed-off-by: Johannes Petzold <jpetzold@pivotallabs.com>
automatic promotion by GoCD workflow LoggregatorIntegrationTest/75 > IntegrationTests/1 > IntegrationTests

tests passed against https://github.com/cloudfoundry/cf-release/commit/a37c9c2888f44a2fd751c82009a3a3c41d62fee7