[decode-syseeprom] fix getattribute check for some platforms

[mykolaf]

Signed-off-by: Mykola Faryma mykolaf@mellanox.com

Fixes: #828
- What I did
For some platforms which implement the eeprom plugin by inheriting from TlvInfoDecoder, the line
t.getattr('read_eeprom_db', None) == None:
results in an error:
AttributeError: 'board' object has no attribute 'getattr'

The cause for that is that TlvInfoDecoder inherits from object, and looks like for object and derived classes there is no __getattr__.
- How I did it

- How to verify it

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

sudo decode-syseeprom
Traceback (most recent call last):
  File "/usr/bin/decode-syseeprom", line 175, in <module>
    exit(main())
  File "/usr/bin/decode-syseeprom", line 58, in main
    or t.getattr('read_eeprom_db', None) == None:
AttributeError: 'board' object has no attribute 'getattr'

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

sudo decode-syseeprom
TlvInfo Header:
   Id String:    TlvInfo
   Version:      1
   Total Length: 573
TLV Name             Code Len Value
-------------------- ---- --- -----

[akokhan]

retest this please

[akokhan]

retest this please

[mykolaf]

The issue was introduced by commit
ATM it's not included in 201911 branch, so there is no need to Include this fix in 201911 branch)

[akokhan]

retest this please

[akokhan]

retest this please

[abdosi]

@mykolaf Please Create PR for 201911 as cherry-pick is not clean

[abdosi]

@mykolaf Remainder again.
@liat-grozovik