Fix creating of mountpath symlink

:Release Notes:
Fix logic for creating of symlink for mountpath
and make calls like listActiveMedia and shardinfo
to return mountpath

:Detailed Notes:
Remove from code create of "/media/mountpoint"
Add checking if symlink already exists

:Testing Performed:

root@goldfinger:~# luna-send -f -n 1  luna://com.palm.db/listActiveMedia '{}'
{
    "returnValue": true,
    "count": 1,
    "media": [
        {
            "deviceId": "1110582131",
            "deviceUri": "\/tmp\/usb\/sda\/sda1",
            "mountPath": "\/media\/mountpoint\/12D1C8E",
            "shardId": "+HoRYV"
        }
    ]
}

root@goldfinger:~# luna-send -f -n 1  luna://com.palm.db/shardInfo '{"shardId": "+HoRYV"}'
{
    "returnValue": true,
    "isActive": true,
    "isTransient": false,
    "shardId": "+HoRYV",
    "deviceId": "1110582131",
    "deviceName": "Drive 1",
    "deviceUri": "\/tmp\/usb\/sda\/sda1",
    "mountPath": "\/media\/mountpoint\/12D1C8E"
}

:QA Notes:

:Issues Address:
[GF-40003] shard mount path is unreliable

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <maxim.sditanov@lge.com>

Change-Id: Ia449c7a52fdf6ebee7ab5a304908101d227ba69e
Reviewed-on: https://g2g.palm.com/3575
Reviewed-by: Build Verification
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>
Tested-by: Maksym Sditanov <maxim.sditanov@lge.com>
Reviewed-by: Igor Kuksyuk <ikuksyuk@luxoft.com>