Make scan_blast_database_directory more robust.
Make scan_blast_database_directory more robust.

close #56

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

elsiklab/sequenceserver,IsmailM/sequenceserver,jasminZ/sequenceserver,elsiklab/sequenceserver,yeban/sequenceserver,jasminZ/sequenceserver,deepakunni3/sequenceserver,IsmailM/sequenceserver,aldermossy/sequenceserver,aldermossy/sequenceserver,IsmailM/sequenceserver,deepakunni3/sequenceserver,yeban/sequenceserver,lepbase/lepbase-sequenceserver,vivekiitkgp/sequenceserver,vivekiitkgp/sequenceserver,lepbase/lepbase-sequenceserver,lepbase/lepbase-sequenceserver,jasminZ/sequenceserver,vivekiitkgp/sequenceserver,yeban/sequenceserver,aldermossy/sequenceserver,elsiklab/sequenceserver,yeban/sequenceserver,deepakunni3/sequenceserver,aldermossy/sequenceserver