Fix options parameter processing in postgres_tablespace.present

[vutny]

What does this PR do?

It makes the options parameter of the postgres_tablespace.present work and report changes if any option was changed. Updated the docsting with meaningful example.

Previous Behavior

The postgres_tablespace.present fails with correctly provided options dictionary.

For example, following state

my_space:
  postgres_tablespace.present:
    - directory: /srv/my_tablespace
    - options:
        seq_page_cost: 1.0
        random_page_cost: 4.0

gives something like this:

[ERROR   ] An exception occurred in this state: Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/salt/state.py", line 1733, in call
    **cdata['kwargs'])
  File "/usr/lib/python2.7/site-packages/salt/loader.py", line 1652, in wrapper
    return f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/salt/states/postgres_tablespace.py", line 124, in present
    for k, v in options:
ValueError: too many values to unpack

And after fixing that issue it leads to this:

[ERROR   ] An exception occurred in this state: Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/salt/state.py", line 1733, in call
    **cdata['kwargs'])
  File "/usr/lib/python2.7/site-packages/salt/loader.py", line 1652, in wrapper
    return f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/salt/states/postgres_tablespace.py", line 142, in present
    set_options={k: v}):
TypeError: tablespace_alter() got an unexpected keyword argument 'set_options'

New Behavior

The postgres_tablespace.present state works with options parameter and reports changes.

----------
          ID: my_space
    Function: postgres_tablespace.present
        Name: my_space
      Result: True
     Comment: Tablespace my_space opts changed
     Started: 11:00:02.593824
    Duration: 1389.75 ms
     Changes:   
              ----------
              my_space:
                  ----------
                  options:
                      ----------
                      random_page_cost:
                          4.0
                      seq_page_cost:
                          1.0

Tests written?

No