Change this line:
if [[ "$TEST" == "ON Master" ]];
To this:
if [ "$TEST" == "ON Master" ];
Details
The issue is the use of [[ .. ]]. The output is showing you the difference. Your value that you're getting for $STATUS is not simply "On Master". It most likely contains other characters, that are most likely not printable so are not being seen.
[[ .. ]]
++ echo On Master
+ TEST='On Master'
+ [[ On Master == \O\N\ \M\a\s\t\e\r ]]
[ .. ]
++ echo On Master
+ TEST='On Master'
+ '[' 'On Master' == 'ON Master' ']'
The use of double square brackets ([[ .. ]]) is discussed here on the TLDP Advanced Bash Scripting pages.
echo $STATUS
This line seems a little suspicious to me as well. I'd protect the contents of $STATUS by wrapping it in double quotes as well.
TEST=`echo "$STATUS"`
Also I'd drop the back ticks ( `...` ) and use the $( ... ) notation instead for executing this command. This change is just a best practice and isn't part of your issue though.
TEST=$(echo "$STATUS")
Control characters in output (^[[92mON^[[0m Master)
Given you're seeing these control characters in your output (^[[92m & ^[[0m) I'm suspicious that the grep command is introducing these into your output in the pipe. It may be that grep is aliases to always include the --color switch, I'd temporarily try calling the executable directly, and by pass any aliases that may be there. Just change the grep to this, /bin/grep.
The presence of these is what we suspected and is why the text was wrapping when you echo the variable $STATUS. These characters are unprintable, and change the color of the terminal to highlight matches that grep has found.
The presence of these also explains why the =~ operator didn't match too. You were trying to match 'On Master' with '^[[92mON^[[0m Master'.
Lastly the colored output with the control characters may be coming from another tool before the grep. I would need to see the actual output from /root/setup_ha to confirm this, but I would be suspicious of that tool as well in producing these characters in the pipe stream.
Stripping the control characters
I found this U&L Q&A titled: Program that passes STDIN to STDOUT with color codes stripped?Program that passes STDIN to STDOUT with color codes stripped?.
Use either of these methods to get rid of the control characters.
Perl
$ cmd-with-colored-output | perl -pe 's/\e\[?.*?[\@-~]//g'
Sed
$ cmd-with-colored-output | sed -r "s/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]//g"
