trunk: mysql unit test failures on dev6 #2255

In http://qa.piwik.org:8080/jenkins/job/Piwik/1539/consoleText, r4293 fails the MYSQLI unit test, but passes with PDO_MYSQL, using PHP 5.3.6.

In http://qa.piwik.org:8080/jenkins/job/Piwik/1540/consoleText, r4293 fails the PDO_MYSQL. using PHP 5.2.17.

(On my Jenkins instance, both tests pass.)

I'm temporarily disabling the CI build, so I can do some troubleshooting in the build directory.

(In [4294]) fixes #2255

• When the LOCAL keyword is omitted from the statement, the unit tests fail on dev6 because the db user doesn't have FILE privilege granted. (Granted.)
• When the LOCAL keyword is included in the statement, the unit tests fail on dev6 because MySQL was not built with --enable-local-infile. (Thus, PDO_MYSQL on dev6 is affected by PHP bug 54158.)

refs #2243

• fixes problem where infile not being deleted when Piwik_Exec() threw an exception (MYSQLI)
• set driver_options uniformly between MYSQLI and PDO_MYSQL
• update unit test conditions (when batch insert should work)
• renamed methods
• the performance gain is worth the effort of trying both LOAD DATA LOCAL INFILE and LOAD DATA INFILE

Excellent improvements of my code, kuddos!