The interface renaming logic fails if one interface is missing.
Because of the `set -e` the whole initramfs hook would abort early on
error.
This change fixes the current behavior to make sure missing interfaces
are properly skipped and ensure existing interface are renamed.
On some products the pci enumeration adds randomness into which nic gets
initialized first.
Because SONiC doesn't use deterministic interface naming but instead old
style interface naming, this leads to eth0 not always being the
management port.
To make sure eth0 is always the management port (SONiC expectation)
rename the interfaces in the initramfs for Arista products.
