- fixes and improvements in GNS:

  - fixed reading of mount object. Should be read not more than PAGE_SIZE - 1,
    reserving one byte for terminating zero.

  - fixed read data zero terminating. Not data[PAGE_SIZE - 1] should be zeroed
    out, but rather zero should be put at the end of actual read data.

  - added one more test which tests how GNS will mount dentry when there is
    number of concurent thread creating entries in the same directory. test_3a

  - fixes in other sanity tests. When a test creates number of concurrent threads
    for checking something, it should wait their termination before getting
    execution result and possibly fail. Do not remove upcalls from /tmp to have
    the ability to look at them after failure.