Make 'os-hosts/node1' case sensitivity defer to DB

RPC is case sensitive, but URL is not, and DB can be. So pull host_name from DB
in HostAPI RPC layer instead of from passed in from URL.  This means RPC will
always get the proper capitalization, and case sensitivity is defined in DB layer.

Fix bug 996879

Change-Id: I448dd4ec3aec4af1adf4487f26ea996db572fa3d
Merge "Make 'os-hosts/node1' case sensitivity defer to DB"