yanglint tests fail for release build

[labuwx]

Hi,

Some tests in yanglint_interactive fail when are run on a release build. The tests in tests/yanglint/interactive/debug.test are only meant to be run on a debug build but the yanglint_debug check in tests/yanglint/interactive/ly.tcl does not do its job since commit 34e2a55. yanglint_debug looks for --debug= in the output of yanglint -h. However since 34e2a55, that string appears in release builds too.

[michalvasko]

Right, the test seems useless anyway, removed.