[VOL-2831] - Multiple adapter support

This commit introduces the necessary APIs needed to support
multiple adapters.  It uses the number of replicas of a given
adapter and consistent hashing to determine the target of a
given request.

The endpoint_manager.go provides two APIs that will be needed
by components communicating over kafka:
 - GetEndPoint() : to be called before sending a request to kafka
 - IsDeviceOwnedByService(): used during device reconciliation

A change is made to the adapter_proxy.go to use this new mechanism
when sending a request to an adapter from another adapter.

The mocks directory was refactored to get around circular package
dependencies.  This implies any component using these mocks will
need to adjust to the new set of directories when using this
library version.

Change-Id: I470cd62fcfd04edc1fd4508400c9619cadaab25a
diff --git a/go.sum b/go.sum
index 2b6007c..aca6e58 100644
--- a/go.sum
+++ b/go.sum
@@ -4,6 +4,8 @@
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 github.com/DataDog/zstd v1.4.1 h1:3oxKN3wbHibqx897utPC2LTQU4J+IHWWJO+glkAkpFM=
 github.com/DataDog/zstd v1.4.1/go.mod h1:1jcaCB/ufaK+sKp1NBhlGmpz41jOoPQ35bpF36t7BBo=
+github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/Shopify/sarama v1.23.1 h1:XxJBCZEoWJtoWjf/xRbmGUpAmTZGnuuF0ON0EvxxBrs=
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 github.com/Shopify/toxiproxy v2.1.4+incompatible h1:TKdv8HiTLgE5wdJuEML90aBgNWsokNbMijUGhmcoBJc=
@@ -23,6 +25,10 @@
 github.com/boljen/go-bitmap v0.0.0-20151001105940-23cd2fb0ce7d/go.mod h1:f1iKL6ZhUWvbk7PdWVmOaak10o86cqMUYEmn1CZNGEI=
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 github.com/bsm/sarama-cluster v2.1.15+incompatible/go.mod h1:r7ao+4tTNXvWm+VRpRJchr2kQhqxgmAp2iEX5W96gMM=
+github.com/buraksezer/consistent v0.0.0-20191006190839-693edf70fd72 h1:fUmDBbSvv1uOzo/t8WaxZMVb7BxJ8JECo5lGoR9c5bA=
+github.com/buraksezer/consistent v0.0.0-20191006190839-693edf70fd72/go.mod h1:OEE5igu/CDjGegM1Jn6ZMo7R6LlV/JChAkjfQQIRLpg=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cevaris/ordered_map v0.0.0-20190319150403-3adeae072e73 h1:q1g9lSyo/nOIC3W5E3FK3Unrz8b9LdLXCyuC+ZcpPC0=
 github.com/cevaris/ordered_map v0.0.0-20190319150403-3adeae072e73/go.mod h1:507vXsotcZop7NZfBWdhPmVeOse4ko2R7AagJYrpoEg=
 github.com/circonus-labs/circonus-gometrics v2.3.1+incompatible/go.mod h1:nmEj6Dob7S7YxXgwXpfOuvO54S+tGdZdw9fuRZt25Ag=
@@ -230,6 +236,8 @@
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+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
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 github.com/spf13/pflag v1.0.1/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
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