Fixed bug that enables official build when environment variable is set to anything (#389)

Author: Elliot Boschwitz

setup.py

@@ -44,7 +44,7 @@ def get_timestamped_version(ver):
     name='mssql-cli',
     author='Microsoft Corporation',
     author_email='[email protected]',
-    version=version if os.environ.get('MSSQL_CLI_OFFICIAL_BUILD', '') \
+    version=version if os.environ.get('MSSQL_CLI_OFFICIAL_BUILD', '').lower() == 'true' \
                     else get_timestamped_version(version),
     license='BSD-3',
     url='https://github.com/dbcli/mssql-cli',