decorrelate phplint and jshint jobs

For MediaWiki core, we always want to run PHP linting but might want to
skip JSHint, for example on the REL1_19 branch which is not passing
Javascript lint tests.

Jobs have been split in JJB with https://gerrit.wikimedia.org/r/48422

Change-Id: I1a1b50381b12c2f9d87622f86a19b0c0068748e5