CA-109295: Allow other_config:hvm_serial to set values other than "pty"

Signed-off-by: John Else <john.else@citrix.com>
Add tests for xapi -> xenopsd HVM metadata conversion

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1475 from siddharthv/NVIDIA-44-CW-LCM

CA-109295: Allow other_config:hvm_serial to set values other than "pty"