Fixes to obmc_boot_test.py:
Fixes to obmc_boot_test.py:

- 'Delete All Sessions' after each boot test to prevent too
  many open connections, i.e. "ConnectionErrors".
- 'Delete Error logs' after each boot test to prevent build-up
  of error logs.

Change-Id: I44b0e6e7145255786583136762598ac8c593e83d
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation