(fast)scan: Solved wierd behavior after removing userbouquets.

When a fastscan or last scanned user bouquet was removed there was some
strange behavior that at a new scan the bouquet did not reappear. You
needed to restart enigma2 before the new bouquet was created and then it
first time this resulted into a bouquets that includes the previous
contants with the new scanned results added, you can even see everything
double.
This was caused because when a userbouquet was removed by the user
interface that only the reference in the rootref was removed.
This solution checks for the reference of a fastscan bouquet or last
scanned bouquet being available in the rootref. When not it will be added
and a new user bouquet will be created or an existing one will be
reopened. When the userbouquet can be created it will always be cleared
first before it is filled with the new scanned services to ensure we do
not have services double or the previous scanned services are still
included.