Only use three jobs for node builds

Author: TheMarex

.travis.yml

@@ -143,7 +143,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=3
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -166,7 +166,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=3
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -189,7 +189,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4 NODE="6"
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Release' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=3 NODE="6"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |
@@ -212,7 +212,7 @@ matrix:
         apt:
           sources: ['ubuntu-toolchain-r-test']
           packages: ['libstdc++-5-dev']
-      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=4 NODE="6"
+      env: CLANG_VERSION='4.0.0' BUILD_TYPE='Debug' ENABLE_MASON=ON ENABLE_LTO=ON ENABLE_NODE_BINDINGS=ON PUBLISH_NODE_BINDINGS=On JOBS=3 NODE="6"
       install:
         - pushd ${OSRM_BUILD_DIR}
         - |