samba-tool: no stack trace on missing ldb tdb

samba-tool: no stack trace on missing ldb tdb

Now, in a testenv, if you forget to use '-s st/ad_dc/etc/smb.conf',
you only see this:

$ bin/samba-tool user rename  dsadsa
ldb: Unable to open tdb '$HERE/st/client/private/secrets.ldb': No such file or directory
ldb: Failed to connect to '$HERE/st/client/private/secrets.ldb' with backend 'tdb': Unable to open tdb '$HERE/st/client/private/secrets.ldb': No such file or directory
Could not find machine account in secrets database: Failed to fetch machine account password from secrets.ldb: Could not open secrets.ldb and failed to open $HERE/st/client/private/secrets.tdb: NT_STATUS_CANT_ACCESS_DOMAIN_INFO
ltdb: tdb($HERE/st/client/private/sam.ldb): tdb_open_ex: could not open file $HERE/st/client/private/sam.ldb: No such file or directory

Unable to open tdb '$HERE/st/client/private/sam.ldb': No such file or directory
Failed to connect to 'tdb://$HERE/st/client/private/sam.ldb' with backend 'tdb': Unable to open tdb '$HERE/st/client/private/sam.ldb': No such file or directory
ERROR(ldb): uncaught exception - Unable to open tdb '$HERE/st/client/private/sam.ldb': No such file or directory

rather than all that AND a stack trace.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>