redirector: migrate sql interface to sqlalchemy

* Replace run_sql queries with SQLAchemy query.

Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>
1: D400 First line should end with '.', not 't'
1: D205 Blank line missing between one-line summary and description
33: D103 Docstring missing
49: D400 First line should end with '.', not ':'
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61: D400 First line should end with '.', not 'e'
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81:41: E261 at least two spaces before inline comment
81:42: E262 inline comment should start with '# '
143: D202 No blank lines allowed *after* function docstring, found 1