[Bug] [Hexagon] RPC Session is not closed properly

[mehrdadh]

In the current state of TVM, when we run hexagon tests on HDK boards and a test fails the session is not properly closed even after deleting the python object.

This is the reason that currently hardware testing is busted. After a test fails, the RPC tracker shows that device is not free and program is halted at starting the session.

Server List
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server-address           key
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  192.168.10.107:2819    server:hexagon-dev
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Queue Status
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key           total  free  pending
-----------------------------------
hexagon-dev   1      0     0
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cc @farshidsp @areusch @kparzysz-quic