set_db_and_ix_paths and ns_server:restart are raceful which may cause couch_db to fail to start

Installing couchbase on a node after uninstalling previous installation with non-default data path gives error "Got no response from save request"
Screenshot attached.

Steps to reproduce:

On a CentOS VM:
1. rm -Rf /opt/couchbase/*
2. rm -Rf /data/*
3. sudo rpm -i couchbase-server-community_x86_64_2.0.0-beta.rpm
4. Setup the cluster with data/index path set to /data and create default bucket
5. Create a couple of documents
6. sudo rpm -e couchbase-server-2.0.0-1723
7. sudo rpm -i couchbase-server-community_x86_64_2.0.0-1888-rel.rpm
8. Setting up the cluster again with data/index path set to /data gives error and couchdb fails to initialize with below crash report


=========================CRASH REPORT=========================
  crasher:
    initial call: couch_db:init/1
    pid: <0.5333.0>
    registered_name: []
    exception exit: {function_clause,
                        [{couch_server,'-terminate/2-fun-0-',
                             [{<<"_replicator">>,<0.693.0>}]},
                         {lists,foreach,2},
                         {gen_server,terminate,6},
                         {proc_lib,init_p_do_apply,3}]}
      in function gen_server:terminate/6
    ancestors: [couch_server,couch_primary_services,couch_server_sup,
                  cb_couch_sup,ns_server_cluster_sup,<0.58.0>]
    messages: []
    links: []
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 610
    stack_size: 24
    reductions: 376
  neighbours:

Diagnostics attached.