There was a wrong assumption that the first call to Popen.poll()
is always None. This is not the case when the process is fast enough
to finish before it gets polled, in which case it is not None, but
it is the return code instead. This caused some executes to have
empty output.

On rare occasion, the previously-used execute() would return
empty output, which would cause the path to change, often resulting
in a 'no such file or directory' error.

Prior to this, it was installing the python libraries in the default
location even if a custom path was given.

Addresses error:
 mysql_connection_unittest.cc: In member function ‘virtual void {anonymous}::MySqlConnectionTest_connectionTimeout_Test::TestBody()’:
 mysql_connection_unittest.cc:633:77: error: ‘mysql_get_option’ was not declared in this scope
      EXPECT_EQ(0, mysql_get_option(mysql, MYSQL_OPT_CONNECT_TIMEOUT, &timeout));

 - moved DHCP{4,6}_DEPRECATED
 - added note to return status text over API