test/*.sh: add explicit error checks/returns

test/*.sh: add explicit error checks/returns

there was an assumption that function calls would terminate early with
an error given 'set -e' was being used. this is true, but only when the
function is part of a simple command otherwise it won't inherit the
behavior. many of the call sites use 'func || return 1' syntax meaning
the function would continue to completion return with the status of the
last command executed. this hid errors with e.g., eval statements. inner
calls within the functions are now explicitly tested for failure.

BUG=aomedia:2669

Change-Id: Ie33a5ac4023dcc800bd302cb8cc54c6c3f2282f5