core: Refactor FenceVdsActionParameters

Refactors FenceVdsActionParameters:
 1) Moves instance attributes before methods
 2) Remove '_' from attribute names
 3) Use constructor chaining
 4) Set default values of instance variables in constructor

Change-Id: I43bc8d5336633cf0f259d08803d2e902be006791
Bug-Url: https://bugzilla.redhat.com/1090799
Signed-off-by: Martin Perina <mperina@redhat.com>