Arista EOS Optimizations and Fixes

[architekture]

Fixes and Updates

• Change version key from internalVersion to version
• Add file detection and verification to the remote_file_copy method
• Update the SSH-native EOS class to better handle optional reloading for OS image installs

[jeffkala]

• Implementing a cleaner and/or flipped based class logic might make sense. Original eos_device.py has always been eAPI "based" eventhough a large percentage of the calls are using native_ssh. With the new SSH driver being built it might make sense to make the SSH driver the base/inherited class and let the eapi (eos_device) driver use those parent methods instead.
• Arista install has appended CLI command options for the reload. Look to implement the conditional logic to use that instead of the dedicated reboot method. (install source flash:foo.bar vs install source flash:foo.bar reload now)