nethserver-samba-migrate-sam: removed getSambaGroupDb() function. Refs #2806

The function failed because the ldb3search command was not provided by
any available package (formerly it came from samba3x*?).
nethserver-samba-migrate-sam: migrate LogonDrive prop. Refs #2811
smb.conf: always use nss idmap backend for local user database. Refs #2815

When acting as PDC use the workgroup name instead of machine name.
nethserver-samba.spec: converted to plain .spec file. Refs #2803
NethServer::Samba perl package: encapsulate workgroup name logic. Refs #2840
nethserver-samba-save event: clear SID from LDAP and secrets.tdb. Refs #2840

This action clears any previously allocated domain SID and machine
password when role is switched between ADS and PDC.  Moreover, if role
is switched again to ADS, a JOIN operation is forced.
Workgroup UI module: Edit workgroup name when role is Workstation. Refs #2803
Domain Users NT group is now mapped to "locals". Refs #2792
nethserver-samba-netcacheflush: clear ID map cache on relevant events. Refs #2792
nethserver-samba-migrate-sam ($useGroupMappingDb): removed unused variable. Refs #2806
nethserver-samba-machine-create: allocate Uid, if not given. Refs #2832
nethserver-samba-migrate-sam: read machine uid from smbpasswd if Uid prop is missing. Refs #2832
nethserver-samba-netcacheflush: fixed shell shebang. Refs #2792
Workgroup/Configure UI module: collapse Workstation fieldset, when unselected. Refs #2803
Merge branch 'b2803'

Refs #2840 #2832 #2815 #2811 #2806 #2803 #2792