Fix warnings and remove statics in neutronvpn-impl

Fix warnings and remove statics in neutronvpn-impl

See inline comments. The major changes were with the NeutronvpnUtils
class which had several public static Maps. The class was refactored
into a singleton class which required injection into many other classes.

Change-Id: Ib2badb6d01c55aab5851c9045d8bea8a911ad0a2
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>