Updated IPC detection logic (#51)

* Added environment variable to enable/disable IPC at runtime

* Fixed IPC detection logic allow for difference process mappings

* Updated README.md

src/rocshmem.cpp

@@ -84,6 +84,8 @@ rocshmem_ctx_t ROCSHMEM_HOST_CTX_DEFAULT;
 
   rocm_init();
 
+  rocshmem_env_config_init();
+
 #ifdef USE_GPU_IB
   CHECK_HIP(hipHostMalloc(&backend, sizeof(GPUIBBackend)));
   backend = new (backend) GPUIBBackend(comm);