typo in argument for format_str_for_message  in autotest.client.shared.utils

after fix:

In [1]: from autotest.client.shared import utils

In [2]: utils.format_str_for_message(msg_str = "nnn")
Out[2]: ' nnn'

In [3]: utils.format_str_for_message("nnn\nffff")
Out[3]: '\nnnn\nffff'

In [4]: utils.format_str_for_message("nnn")
Out[4]: ' nnn'

In [5]: utils.format_str_for_message(sr = "nnn")
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-b89509bfa590> in <module>()
----> 1 utils.format_str_for_message(sr = "nnn")

TypeError: format_str_for_message() got an unexpected keyword argument 'sr'

Signed-off-by: Vijaykumar Jain <vijaykumar.tater@gmail.com>