Add session-clearing to all tests that need it
Add session-clearing to all tests that need it

Add test for logout (clearing a session) in the source
unit tests. Also clear sessions in integration tests
whenever a source/journalist is probably going to
close their browser.

heartsucker/securedrop,jaseg/securedrop,pwplus/securedrop,heartsucker/securedrop,ageis/securedrop,kelcecil/securedrop,jaseg/securedrop,kelcecil/securedrop,kelcecil/securedrop,ageis/securedrop,GabeIsman/securedrop,pwplus/securedrop,pwplus/securedrop,chadmiller/securedrop,ehartsuyker/securedrop,conorsch/securedrop,harlo/securedrop,harlo/securedrop,chadmiller/securedrop,harlo/securedrop,jaseg/securedrop,jrosco/securedrop,jrosco/securedrop,harlo/securedrop,jaseg/securedrop,ageis/securedrop,GabeIsman/securedrop,harlo/securedrop,jrosco/securedrop,jeann2013/securedrop,garrettr/securedrop,jaseg/securedrop,conorsch/securedrop,GabeIsman/securedrop,micahflee/securedrop,GabeIsman/securedrop,GabeIsman/securedrop,pwplus/securedrop,ehartsuyker/securedrop,conorsch/securedrop,GabeIsman/securedrop,garrettr/securedrop,conorsch/securedrop,jaseg/securedrop,jeann2013/securedrop,ehartsuyker/securedrop,micahflee/securedrop,heartsucker/securedrop,jrosco/securedrop,ageis/securedrop,jrosco/securedrop,kelcecil/securedrop,jeann2013/securedrop,micahflee/securedrop,heartsucker/securedrop,garrettr/securedrop,kelcecil/securedrop,jeann2013/securedrop,chadmiller/securedrop,ehartsuyker/securedrop,jeann2013/securedrop,jrosco/securedrop,jeann2013/securedrop,garrettr/securedrop,pwplus/securedrop,chadmiller/securedrop,kelcecil/securedrop,chadmiller/securedrop,pwplus/securedrop,micahflee/securedrop,harlo/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,chadmiller/securedrop,ehartsuyker/securedrop