jdbc-mapping gfsh commands should accept '/' in front of region name

The jdbc-mapping gfsh commands should work the same as typing region name without the prefix '/'

Current behavior:

gfsh>create jdbc-mapping --region=/LargeRegion --data-source=datasource --pdx-name="LargeTableDemo" --table=largetable
A region named /LargeRegion must already exist.

gfsh>create jdbc-mapping --region=LargeRegion --data-source=datasource --pdx-name="LargeTableDemo" --table=largetable
(Experimental)

Member | Status | Message
------- | ------ | ------------------------------------------------------
server1 | OK | Created JDBC mapping for region LargeRegion on server1
server2 | OK | Created JDBC mapping for region LargeRegion on server2

Changes to configuration for group 'cluster' are persisted.