Fix javadoc comments

[matgallacher]

Javadoc specs have changed and compilation fails with the following issues with java 8

C:\Repos\Volley\volley\src\main\java\com\android\volley\toolbox\BasicNetwork.java:268: error: malformed HTML * Converts Headers[] to Map. ^ C:\Repos\Volley\volley\src\main\java\com\android\volley\toolbox\BasicNetwork.java:268: error: bad use of '>' * Converts Headers[] to Map. ^ C:\Repos\Volley\volley\src\main\java\com\android\volley\VolleyLog.java:40: error: self-closing element not allowed *
^ C:\Repos\Volley\volley\src\main\java\com\android\volley\VolleyLog.java:42: error: self-closing element not allowed *
^ C:\Repos\Volley\volley\src\main\java\com\android\volley\VolleyLog.java:28: error: self-closing element not allowed *

^ C:\Repos\Volley\volley\src\main\java\com\android\volley\VolleyLog.java:29: error: self-closing element not allowed * to see Volley logs call:
^

[jpd236]

It seems like Java 8 made Javadoc linting the default, though I don't believe the specs themselves have changed (in other words, we can just fix these and they will still make sense with older compilers).

Probably just need to use {@code Headers[]} and {@code Map<String, String>} in BasicNetwork and change the <br />s to <br>s and <p/>s to <p>s in VolleyLog. PR welcome.