REBASE jenkins script
set WAL journal size limit to 10% of available space or 10M

Previously, there was no limit to the size of the WAL log file, and under
heavy load, it could grow quite a bit.  This sets a limit as either 10Megs
or 10% of the available space, whichever is larger.

refs #555 https://dev.guardianproject.info/issues/555
PRAGMA synchronous = NORMAL for higher reliability

Using the WAL mode should reduce the performance hit of using sync mode
enough to be usabel.

https://www.sqlite.org/pragma.html#pragma_synchronous

fixes #3662 https://dev.guardianproject.info/issues/3662
rename sql_key --> pthread_key to avoid confusion with db key

sql_key stores the pthread thread-specific key for retreiving sqlfs
pointers from the thread-specific store.  sql_key can easily be confused
for the key for the sqlcipher database.
zero out database key when done using it

This commit zeros out the stored password when the last instance is closed.
The password has to be stored for multi-threaded mode, since new threads
will need the password in order to access the database.

refs #3402 https://dev.guardianproject.info/issues/3402
REBASE zero out database key when done using it
REBASE set WAL journal size limit to 10% of available space or 10M
REBASE jenkins script