There are cases when clients cannot build a trust chain in order to
verify ESX certificate. The SSL thumbprint is always available and it is
the preferred way for verifying the connection when doing NFC transfer.
This patch replace the usage of truststore with SSL thumbprints in
VmdkReadHandle and VmdkWriteHandle.
Change-Id: I9573bada15aef2bf8d25fa824bbbc2b421586733