update link to VPN instruction
update link to VPN instruction

Signed-off-by: Tobias Zipfel <087edddb12ac44c92ffe5bde7e37fdd0c506a257@de.ibm.com>

cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service