Obfuscate TACACS key in show run all and show tacacs

[taoyl-ms]

- What I did
Obfuscate TACACS passkey in show run all and show tacacs output.
Please note that in DB the passkey is still in clear text.

- Previous command output (if the output of a command-line utility has changed)

admin@sonic:~$ show tacacs
TACPLUS global auth_type login
TACPLUS global timeout 5 (default)
TACPLUS global passkey mypasskey

TACPLUS_SERVER address 10.0.0.1
               priority 1
               tcp_port 49

TACPLUS_SERVER address 10.0.0.2
               priority 1
               tcp_port 49

- New command output (if the output of a command-line utility has changed)

admin@sonic:~$ show tacacs
TACPLUS global auth_type login
TACPLUS global timeout 5 (default)
TACPLUS global passkey my******

TACPLUS_SERVER address 10.0.0.1
               priority 1
               tcp_port 49

TACPLUS_SERVER address 10.0.0.2
               priority 1
               tcp_port 49

-->

[nikos-github]

Have you looked at a way to not have a cleartext key in the db? redis-cli is not privileged. It can be run by anyone by default. This is a security issue. One-way hash for example can be used.