prepare_data.sh: snowcli fixes

[sfc-gh-vtimofeenko]

Running the prepare_data.sh results in:

Errors from snowcli

``` DeprecationWarning: The command 'stage' is deprecated. `snow object stage` command group is deprecated. Please use `snow stage` instead. DeprecationWarning: The command 'copy' is deprecated.

    An unexpected exception occurred. Use --debug option to see the traceback. Exception message:
    
    001003 (42000): 01b5c6bb-0605-12ce-0057-53030429dcda: SQL compilation error:
    syntax error line 1 at position 140 unexpected '<'.
    syntax error line 1 at position 146 unexpected '.'.
    syntax error line 1 at position 153 unexpected '.'.
    syntax error line 1 at position 165 unexpected 'object'.
    syntax error line 1 at position 175 unexpected '0x10999d970'.
    DeprecationWarning: The command 'stage' is deprecated.
    `snow object stage` command group is deprecated. Please use `snow stage` instead.
    DeprecationWarning: The command 'copy' is deprecated.
    
    An unexpected exception occurred. Use --debug option to see the traceback. Exception message:
    
    001003 (42000): 01b5c6bb-0605-12ce-0057-53030429dcde: SQL compilation error:
    syntax error line 1 at position 135 unexpected '<'.
    syntax error line 1 at position 141 unexpected '.'.
    syntax error line 1 at position 148 unexpected '.'.
    syntax error line 1 at position 160 unexpected 'object'.
    syntax error line 1 at position 170 unexpected '0x103b9dc70'.
    DeprecationWarning: The command 'stage' is deprecated.
    `snow object stage` command group is deprecated. Please use `snow stage` instead.
    DeprecationWarning: The command 'copy' is deprecated.
    
    An unexpected exception occurred. Use --debug option to see the traceback. Exception message:
    
    001003 (42000): 01b5c6bb-0605-144e-0057-53030429f926: SQL compilation error:
    syntax error line 1 at position 150 unexpected '<'.
    syntax error line 1 at position 156 unexpected '.'.
    syntax error line 1 at position 163 unexpected '.'.
    syntax error line 1 at position 175 unexpected 'object'.
    syntax error line 1 at position 185 unexpected '0x1079e5ac0'.

</details>

These two commits:

- Add shell script error "handling" (halt and catch fire on error, don't proceed)
- Update snowcli syntax to match current (2.6.1) version