[ACM] Fix the resource representations in the resource_label

[ACM] Fix the resource representations in the resource_label
file. Without this patch, multiple representations of the same
resource can co-exist in the resource label file and lead to errors
during operation.

Ensures that all resource file names are stored with absolute
path name and are unique. Setting labels of phy-resources, relative
paths will automatically be pre-pended with '/dev/'; labeling
file-resources with relative paths will raise an error.

Signed-off by: Reiner Sailer <sailer@us.ibm.com>