Initializing a longer resource id in DB2 nosql backend

Longer resource id is reqpured by compute node's resource as their
id is '<hostname>_<nodename>'. DB2 creates a VARCHAR(70) for
resource id when its length < 70. But DB2 can create a VARCHAR(n)
for the resource id which has n(n>70) characters. This patch adds
an option 'db2nosql_resource_id_maxlen'(default is 512) to allow
user to adjust the value for their ENV.

@DocImpact

Change-Id: Ib58cfffb238d3b818831f0ccfe4659cfcf9c3c8a
Closes-Bug: #1387532
Merge "Initializing a longer resource id in DB2 nosql backend"