boards without mbed.htm is not detected anymore

[jupe]

Looks that #335 fixes one bug but leads to another:
Boards that doesn't have mbed.htm in mount point is no more detected by default. See logs:

$ mbedls -u
WARNING:mbedls.platform_database:Duplicate platform ids found: daplink.0461 daplink.0462 daplink.0457, ignoring the definitions from /home/user/.local/share/mbedls/platforms.json
WARNING:mbedls.lstools_base:Marking device with mount point "/mnt/platform-3f980000_usb-usb-0_1_4_1_0-scsi-0_0_0_0" as unmounted due to the following error: [Errno 2] No such file or directory: '/mnt/platform-3f980000_usb-usb-0_1_4_1_0-scsi-0_0_0_0/mbed.htm'
+---------------+----------------------+-------------+--------------+--------------------------------------------------+-----------------+
| platform_name | platform_name_unique | mount_point | serial_port  | target_id                                        | daplink_version |
+---------------+----------------------+-------------+--------------+--------------------------------------------------+-----------------+
| K66F          | K66F[0]              | unknown     | /dev/ttyACM0 | 0311000033514e45000d5015846c00176cb1000097969900 | unknown         |
+---------------+----------------------+-------------+--------------+--------------------------------------------------+-----------------+

[bridadan]

Internal Arm reference: IOTMORF-2382

[ciarmcom]

ARM Internal Ref: MBOTRIAGE-472