[CLI][show][platform] Added ASIC count in the output. (#1185)

[smaheshm]

- What I did

Added platform ASIC count output to platform summary. Also added option for JSON output.
Note: This is a merge from "master".

- How I did it

Added ASIC count in hardware info.

- How to verify it

Manual CLI verification.

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

admin@str-s6000-acs-9:~$ show platform summary 
Platform: x86_64-dell_s6000_s1220-r0
HwSKU: Force10-S6000
ASIC: broadcom

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

admin@str-s6000-acs-9:~$ show platform summary 
Platform: x86_64-dell_s6000_s1220-r0
HwSKU: Force10-S6000
ASIC: broadcom
ASIC Count: 1
admin@str-s6000-acs-9:~$ show platform summary --json
{
  "asic_count": 1, 
  "asic_type": "broadcom", 
  "hwsku": "Force10-S6000", 
  "platform": "x86_64-dell_s6000_s1220-r0"
}

admin@str-nswitch-acs-2:/usr/lib/python2.7/dist-packages/utilities_common$ show platform summary
Platform: x86_64-nswitch-r0      
HwSKU: nswitch                          
ASIC: broadcom
ASIC Count: 6                              
admin@str-n3164-acs-2:/usr/lib/python2.7/dist-packages/utilities_common$ show platform summary --json
{                    
  "asic_count": 6,
  "asic_type": "broadcom",               
  "hwsku": "nswitch",
  "platform": "x86_64-nswitch-r0"
}  

[smaheshm]

retest this please

[smaheshm]

@abdosi Is the failure in pytest expected?

[abdosi]

LGTM