THRIFT-4328: disable centos-7.3 build jobs which appear to be unstable/hang in jenkins

This closes #1358
diff --git a/.travis.yml b/.travis.yml
index 960ba97..e372e13 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -59,20 +59,22 @@
 
     # Autotools builds
     # TODO: Remove them once migrated to CMake
-    - TEST_NAME="Autotools (CentOS 7.3)"
-      DISTRO=centos-7.3
-      SCRIPT="autotools.sh"
-      BUILD_ENV="-e CC=gcc -e CXX=g++"
-      BUILD_ARG="--without-cpp --without-csharp --without-c_glib --without-d -without-dart --without-erlang --without-go --without-haskell --without-haxe"
+    # centos-7.3 build jobs appear to be unstable/hang...
+    # TEST_NAME="Autotools (CentOS 7.3)"
+    # DISTRO=centos-7.3
+    # SCRIPT="autotools.sh"
+    # BUILD_ENV="-e CC=gcc -e CXX=g++"
+    # BUILD_ARG="--without-cpp --without-csharp --without-c_glib --without-d -without-dart --without-erlang --without-go --without-haskell --without-haxe"
 
     - TEST_NAME="Autotools (Ubuntu Xenial)"
       SCRIPT="autotools.sh"
       BUILD_ENV="-e CC=gcc -e CXX=g++"
-      BUILD_ARG="--enable-plugin --without-java --without-lua --without-nodejs --without-perl --without-php --without-php_extension --without-python --without-py3 --without-ruby --without-rust"
+      BUILD_ARG="--enable-plugin" # --without-java --without-lua --without-nodejs --without-perl --without-php --without-php_extension --without-python --without-py3 --without-ruby --without-rust"
 
     # CMake builds
-    - TEST_NAME="CMake (CentOS 7.3)"
-      DISTRO=centos-7.3
+    # centos-7.3 build jobs appear to be unstable/hang...
+    # TEST_NAME="CMake (CentOS 7.3)"
+    # DISTRO=centos-7.3
 
     - TEST_NAME="CMake (Ubuntu Xenial)"
 
@@ -81,7 +83,7 @@
       BUILD_LIBS="CPP TESTING TUTORIALS"
       BUILD_ARG="-DWITH_BOOSTTHREADS=ON -DWITH_PYTHON=OFF -DWITH_C_GLIB=OFF -DWITH_JAVA=OFF -DWITH_HASKELL=OFF"
 
-    - TEST_NAME="C++ Plugin (Std Thread)"
+    - TEST_NAME="C++ (Std Thread) and Plugin"
       BUILD_LIBS="CPP TESTING TUTORIALS"
       BUILD_ARG="-DWITH_PLUGIN=ON -DWITH_STDTHREADS=ON -DWITH_PYTHON=OFF -DWITH_C_GLIB=OFF -DWITH_JAVA=OFF -DWITH_HASKELL=OFF"
 
@@ -94,10 +96,10 @@
 
     # C and C++ undefined behavior. This wraps autotools.sh, but each binary crashes if
     # undefined behavior occurs. Skips the known flaky tests.
-    # Unstable: THRIFT-4064 needs to be fixed perhaps
+    # Unstable: THRIFT-4064 needs to be fixed perhaps?
     - TEST_NAME="UBSan"
       SCRIPT="ubsan.sh"
-      BUILD_ARG="--without-haskell --without-js --without-nodejs --without-perl --without-python"
+      BUILD_ARG="--without-haskell --without-nodejs --without-perl --without-python"
       UNSTABLE=true
 
 matrix: