With the recent version vCenter 7.0.0b there seems still being an issue when having HTTP / HTTPS proxy configured and trying to import an OVA / OVF.
This is the error message you will see most likely:
Failed to deploy OVF package. ThrowableProxy.cause A general system error occurred: Transfer failed: Server not trusted: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target, note that HTTP/s proxy is configured for the transfer.
A quick workaround is to disable Proxy via VAMI and only enable it when you need id to download updates via Lifecycle Manager or for vCenter updates.
I have a support case open for this, let´s see if there will be a fix soon.
Update, there is a KB out at VMware that you need to specify NO_PROXY according to your environment to get this working again.