[Task] Use string constant for Open/Set URI

Define string constants for action and parameters, for
Open/Open Next/Set URI API instead of duplicating the strings
parameters.

Signed-off-by: Ludovic Ferrandis <ludovic.ferrandis@intel.com>
[Coding Convention] Fix tabulation

Signed-off-by: Ludovic Ferrandis <ludovic.ferrandis@intel.com>