Clean up shell display of slave info

Suppress links and improve display of slave information for the 'show' and
'create' commands. Also refactor shell.py to avoid repeating the code for
displaying an instance.

The revised print_instance method also avoids bug 1322822 where the order
in which attributes are queried can affect the display output.

Depends-On: If8a154083d0095606fb3ee115cc9b66ab788cbb4

Partially-Implements: blueprint replication-v1
Partial-Bug: 1322822
Change-Id: Ie1ac42d61e920ac8ea1ebab35c2db096fd313077
Merge "Clean up shell display of slave info"