Use INSTALL_PATH env variable to set rocksDB installtion path instead of using sed hack

CMAKE_CXX_FLAGS_RELEASE already defines "-DNDEBUG" and "-O3".
We set them just to be sure that even in older/newer version of Cmake
they are set correctly

Problem: If one of the donwload task fails the script do not stop and
the other task continue to donwload sources.

Solution: If one of the task fails, print an informative error message
and send a signal to the parent process that kills all the spawned tasks
and exits with error code.

In case the glibc could not be loaded through dlopen print the relative
error and exit from the client

Also, startup and shutdown scripts now have a new argument
to decide on where the created pssh hostfile is stored.

It is only relevant for sparse files but the current implementation
has a too high overhead on a single node (~10%). We need to find
a better solution at a later point.

This is an optimization for mdtest which shows very slow performance
in removing files, getting worse with an increasing number of nodes.

Since the introduction of required parameters wasn't possible to show
the help message.
In fact the --help flag was checked after all other parameters.

mdtest summary calculation of multiple iterations might be flawed.
Also Daemon is restarted for each iteration.

Postpone the creation of the OpenFile object until we are sure that the
file actually exists and we have enough access rigths for it.

Problem:
In the case the path for which the check access is performed doesn't
exists the server will set `out.err` with the correct error number (ENOENT).
On client side the value of out.err is used as return value but the
errno variable is not set.

Assert is put after a more detailed error message is written to the log.

Previously, host rpc addresses have been looked up lazily when a request
was done. This is not necessary as all hosts are looked up anyways
while the file system is running.

Now, all RPC addresses are looked up when the environment is initialized.
After that, the rpc_address map is only accessed read-only and does not
require a mutex anymore.

Since POSIX.1-2001 the S_IFMT (0170000) bitmask of the file mode must
contain the file type.

At the moment we correctly support
 - [S_IFREG] regular file
 - [S_IFDIR] directory

Previously, clients would look for the daemon by name which was not robust.
If the daemon was started with valgrind for example, clients would not find
the daemon.

Similar to other applications a daemon now creates a pid file with
information about its pid and its started mountdir.

Proper errorhandling on server and client side was added.

Multiple daemons per node are explicitly not allowed for now!

Previously, we gave already installed libfabric versions no chance
to be detected over exclusively installed libfabric

Review and fixes that died when rebasing all commits