Replace hardcoded device number to value returned by root device finder
Replace hardcoded device number to value returned by root device finder

Signed-off-by: Yulia Gaponenko <d7604262e9d9d4ab94e4733c971152f424a52fb1@ru.ibm.com>

gu-bin/bosh-agent,cloudfoundry/bosh-agent,gu-bin/bosh-agent,mattcui/bosh-agent,cloudfoundry/bosh-agent,mattcui/bosh-agent,mattcui/bosh-agent,gu-bin/bosh-agent