config command does not accept abbreviation

[qiluo-msft]

Description

Steps to reproduce the issue
1.

admin@sonic:~$ sudo config interf startup Ethernet2

Describe the results you received

Usage: config [OPTIONS] COMMAND [ARGS]...

Error: No such command "interf".

Describe the results you expected
It should support command abbreviation.

Additional information you deem important (e.g. issue happens only occasionally)

Output of show version

SONiC Software Version: SONiC.20181130.20
Distribution: Debian 9.9
Kernel: 4.9.0-8-amd64
Build commit: ea1a21d
Build date: Tue May  7 07:59:02 UTC 2019
Built by: sonicbld@jenkins-slave-phx-3

Docker images:
REPOSITORY                 TAG                 IMAGE ID            SIZE
docker-syncd-brcm          20181130.20         3a92a514fc96        361MB
docker-syncd-brcm          latest              3a92a514fc96        361MB
docker-orchagent-brcm      20181130.20         4a4e0b959307        286MB
docker-orchagent-brcm      latest              4a4e0b959307        286MB
docker-lldp-sv2            20181130.20         01c23b57577c        274MB
docker-lldp-sv2            latest              01c23b57577c        274MB
docker-dhcp-relay          20181130.20         c2fcb935dc7e        256MB
docker-dhcp-relay          latest              c2fcb935dc7e        256MB
docker-database            20181130.20         af6a03ecc883        255MB
docker-database            latest              af6a03ecc883        255MB
docker-teamd               20181130.20         384afb01b8fa        274MB
docker-teamd               latest              384afb01b8fa        274MB
docker-snmp-sv2            20181130.20         d9b6f79bb453        289MB
docker-snmp-sv2            latest              d9b6f79bb453        289MB
docker-router-advertiser   20181130.20         161a2bf893a8        254MB
docker-router-advertiser   latest              161a2bf893a8        254MB
docker-platform-monitor    20181130.20         c65fd90fc91e        286MB
docker-platform-monitor    latest              c65fd90fc91e        286MB
docker-fpm-quagga          20181130.20         4e31139f8d11        281MB
docker-fpm-quagga          latest              4e31139f8d11        281MB