floss: Create PID file when gd shim is init

gd idle module and gd shim module both get initialized on start up which
makes btmanagerd think that the adapter is enabled, disabled and then
enabled again (looking at PID files). Moving the pid creation to just
the gd shim module prevents this and only a single Enable event is seen.

Bug: 193070105
Test: btclient enable and verify only 1 callback seen
Tag: #floss
Change-Id: Ic6a79ab9c8d8e04f974443776c7639c7f7f0b2ec