refactor: start_docker()

[AkshayAwate]

Running a command and then checking its exit status with $? against 0 is redundant.
More info can be found: https://www.shellcheck.net/wiki/SC2181
If this is good to go, then we can refactor other functions code too.
Thanks

[prashant-shahi]

Thanks for the pull request!

Can you also address similar ones in line number 268, 272 and 290?

[Line 268:](javascript:setPosition(268, 15))
        if (( $EUID != 0 )); then
              ^-- [SC2004](https://www.shellcheck.net/wiki/SC2004) (style): $/${} is unnecessary on arithmetic variables.
 
[Line 272:](javascript:setPosition(272, 19))
            if [[ $? -ne 0 ]] && ! $sudo_cmd -v; then
                  ^-- [SC2181](https://www.shellcheck.net/wiki/SC2181) (style): Check exit code directly with e.g. 'if ! mycmd;', not indirectly with $?.
 
[Line 290:](javascript:setPosition(290, 7))
if (( $EUID != 0 )); then
      ^-- [SC2004](https://www.shellcheck.net/wiki/SC2004) (style): $/${} is unnecessary on arithmetic variables.
 
[Line 307:](javascript:setPosition(307, 7))
if [[ $? -ne 0 ]]; then
      ^-- [SC2181](https://www.shellcheck.net/wiki/SC2181) (style): Check exit code directly with e.g. 'if ! mycmd;', not indirectly with $?.

[AkshayAwate]

@prashant-shahi since there is no arithmatic calculation involved using $EUID, we can ignore refactoring
L268 and L290

[sonarcloud]

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[prashant-shahi]

@AkshayAwate shellcheck was asking to use EUID instead of $EUID for the arithmetic operation.
But anyways, we can address that and other best practices later.

[welcome]

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