[techsupport] [202106] Removed -i option for docker commands and Impr…

…oved Error Reporting (#1843)

What I did
Fix: sonic-net/sonic-buildimage#8850

Issue was introduced by #1723, #1833, and #1843 (pending merge)

The error_handler is a great idea but the bash script needs to be error free first.

How I did it
Fix bash script errors.

How to verify it
run show techsupport test..

Signed-off-by: Ying Xie <ying.xie@microsoft.com>