Silence error logging while running tests that are intended to produce errors

The errors in the test log are distracting, making it look like
a test actually failed.
    add buffer based rc
Merge pull request #1159 from ruil2/scc_rc_1

    add buffer based rc
add interface UT for ForceIntraFrame
remove blank lines
Merge pull request #1162 from sijchen/interfaceUT11

[Encoder] add interface UT for ForceIntraFrame
Remove an unused variable

This fixes build warnings with clang on OS X.
Merge pull request #1153 from mstorsjo/silence-error-testing

Silence error logging while running tests that are intended to produce errors
Merge pull request #1167 from mstorsjo/remove-unused-variable

Remove an unused variable
Merge remote-tracking branch 'upstream/master' into travis.osx