Fix bug while deleting the database connection

[Taherpatrawala]

Related to #3361

When we get a del_msar_schema from the client side we get a string value "true"/"false" hence the condition to check this variable always considers it to be true and deletes the database connection, so I made another check further to check the string value.
I am unsure whether I should change the exception after hearing from @mathemancer

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[Anish9901]

Good work so far @Taherpatrawala! I've updated the expected behavior for part 2 of the issue factoring in @mathemancer's comment about the error behavior, please take a look.

[Anish9901]

@Taherpatrawala issue #3361 is a high priority for us, could you make the required changes within a couple of days?

[Taherpatrawala]

@Anish9901 On it! Should I create a separate exception in database_exceptions/exceptions.py ?

[Anish9901]

@Taherpatrawala We've decided to handle Part 2 of the issue in a subsequent PR, your implementation of Part 1 of the issue looks good, and I've added a test in 4b138eb to ensure that it works as intended.

Thanks for your contribution!