- fixes about cobd_switch() which caused issues with cleanup:

  - avoid double connections to choosen export due to using lctl on umounted client (1st connection) and after that mount the client (2nd connection). Avoid double EA init along with double connection.

  - disconnect correct export on cobd_disconnect()

- avoid possible oops on double cobd_cleanup() due to freed cmobd->write_srv, but not zerod out after that.
- in cobd_switch() set ->cache_on field into new value only if COBD_CONNECT or COBD_SWITCH bias is specified.

- in LMV and LOV in lconf cleanup LMV and LOV first and after that cleanup all their targets. This is because LMV, etc. cleanup needs targets OBD attached, with correct obd_name, etc. This fixes prevents oops in disconnect time whrn using test45 configuration.