CLOUDSTACK-5296: Add certificate chain support for netscaler

This patch adds support for trust chains in the netscaler.

I initially planned on using the 10.1 API's "bundle" feature but during
my testing I found that was not working. So I am doing the chain linking
myself. Also NS can have only one entity of a certificate ie lets say
two different users try to add the same certificate on the netscaler
only one of them will go through. The other one says resouce already
exists even though they have different files.

This can be a problem in trust chains where the chain can be shared
between multiple accounts/certificates. So, I am using the figerprint as
an identifier of a certificate and making sure that we delete it only
when no one references it.
 after XS host reboot, all SG rules are gone, need to check if SG rules frame is there when program  rules for VM, if not , create the SG rule frame