sap_hdbsql: Add error handling and secure flags for hdbsql

[marcelmamula]

Changes

• Added better handling for errors reported in sap_hdbsql - Except errors #51 by @crysaki
• Added better handling for changed_when: Logic for C(changed): If C(filepath) is used, C(changed) is always true. If C(query) is used, C(changed) is true only if at least one query is not a C(SELECT) statement.
• Added secure flags proposed in sap_hdbsql module: SECURE Connection #41 by @stm85
• Added comment to explain pitfalls of using become_flag reported in sap_hdbsql: Fail with wrong become_flag ignoring system python #48

These changes were wrapped in light refactoring for clarity.

Tests

Tested on SLES_SAP 16.0 running BW4HANA database.

Authentication error

        failed: true
        msg: SAP HANA Authentication Failed. Please check credentials/userstore.
        rc: 3
        stderr: |-
            * 10: authentication failed SQLSTATE: 28000

Authorization error:

        failed: true
        msg: 'SAP HANA Authorization Error: The user has insufficient privileges to perform
            this action.'
        rc: 3
        stderr: |-
            * 258: insufficient privilege: Detailed info for this error can be found with guid '250306B97F15FC499AB54C649BEF6B63' SQLSTATE: HY000

[sean-freeman]

LGTM - sensible update and well defined tests