Decode idrac_firmware into array of hashes

idrac_firmware is going to be a string.  Decode it before use.

Also a bug fix around forced_restart that was a string and not bool
Can you just change force_restart to be a boolean in the type, like here:

https://github.com/dell-asm/dell-idrac/blob/53047830e3a93d2e88264a0ec8ba6413dfa1936a/lib/puppet/type/idrac_fw_update.rb#L23