[libmultipath] load default hwtable entries not overriden by configlets

[libmultipath] load default hwtable entries not overriden by configlets

Rationale from Edward Goggin, EMC :

"
I'm wondering why when I put "device {}" entries in the multipath conf file
I
lose all of the other entries setup in the libmultipath/hwtable.c file.
Devices
which do not match the vendor and model strings of the device entries I
setup in the conf file are all forced to pick up default multipath
attributes.

This approach forces me to know the attributes for all vendor/model device
types in my SAN configuration whenever I want to setup even a small change
in the device attributes for a single device type.

I would rather see the that the entries that are setup in the conf file
simply
override the ones setup in the hwtable.c file.  Yet, entries already setup
in
the hwtable.c file which are not overridden remain valid.  The only devices
which pick up defaults are ones for which there is not a device entry in
either the libmultipath/hwtable.c file or the multipath conf file.
"