[SDNVPN] Add helper functions to create bgpvpn and associations
[SDNVPN] Add helper functions to create bgpvpn and associations

JIRA: FUNCTEST-99

These functions are used by sdnvpn test cases
to create vpns and network associations

Change-Id: I2fb25c84d8d02ea1cc92677e6a33e469a5d3ddc3
Signed-off-by: Nikolas Hermanns <2cd021a965d1d36ef14beefd1f655dcc55f50bc1@ericsson.com>

mywulin/functest,opnfv/functest,mywulin/functest,opnfv/functest