Executor多占用分片资源导致资源浪费问题

[haocao]

将Executor默认占用资源设置为Cpu0.1，Memory32MB

[hanahmily]

Mesos源代码中将这两个值定位常量，编译期与运行期均不可修改

// Default cpu resource given to a command executor.
constexpr double DEFAULT_EXECUTOR_CPUS = 0.1;

// Default memory resource given to a command executor.
constexpr Bytes DEFAULT_EXECUTOR_MEM = Megabytes(32);