BUG/MINOR: peers: fix internal/network key type mapping.

BUG/MINOR: peers: fix internal/network key type mapping.

Network types were directly and mistakenly mapped on sample types:

This patch fix the doc with values effectively used to keep backward
compatiblitiy on existing implementations.

In addition it adds an internal/network mapping for key types to avoid
further mistakes adding or modifying internals types.

This patch should be backported on all maintained branches,
particularly until v1.8 included for documentation part.