restapi: VM helper as static method

This class simulates a resource using internal Resteasy injection
implementation. This doesn't work in newer versions of Resteasy. To
avoid that this patch converts it into static methods. Not very nice,
will be reworked in the future.

Change-Id: I6710f8acd2da463303218f596b57747b0622a475
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>