t3200 (branch): fix '&&' chaining

t3200 (branch): fix '&&' chaining

Breaks in a test assertion's && chain can potentially hide failures
from earlier commands in the chain.  Fix these breaks.

The 'git branch --help' in the test may fail if git manual pages are
not installed, but the point of the test is to make sure it does not
create a bogus branch "--help", so run it under 'test_might_fail'.

Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>