fix travis build on osx

tools/travis/travis_osx_before_install.sh

@@ -5,6 +5,7 @@ if [ $ANALYZE = "true" ]; then
     echo "Skipping static analysis for OS X"
     exit 0
 else
+    brew update
     brew install check
     brew install userspace-rcu
     brew install valgrind

tools/travis/travis_osx_script.sh

@@ -9,7 +9,6 @@ else
     export OPENSSL_ROOT_DIR="/usr/local/opt/openssl"
     export PATH="/Users/travis/Library/Python/2.7/bin:$PATH"
 
-
     echo "Documentation and certificate build"  && echo -en 'travis_fold:start:script.build.doc\\r'
     mkdir -p build && cd build
     cmake -DCMAKE_BUILD_TYPE=Release -DUA_BUILD_EXAMPLES=ON -DUA_BUILD_SELFSIGNED_CERTIFICATE=ON ..