Ignore secure boot attribute for IBMi guests

The secure boot support setting is checked in CORE only for IBMi, but not for RPA partitions(AIX/Linux) since Novalink treats AIX and Linux the same way. Due to this, the deploys seem to fail even if a IBMi deploy is attempted by using a template that has secure boot option disabled as this attribute is blocked at the schema level.

Based on the discussion, it turns out that this cannot be fixed in NL/HMC REST layers and the behavior is right based on how PHYP and HMC work.

Hence, in case of IBMi VM deploys the secure boot attribute shouldn't be part of the request at all and the proposed fix as part of this defect will ignore setting this attribute in the schema in such cases.