Fix unit test regressions with Paramiko 2.7+.
Fix unit test regressions with Paramiko 2.7+.

Paramiko 2.7 introduced new parsing logic for RSA/DSA private keys, and
this logic is far more sensitive to newlines. We previously had our
sample private keys for unit tests formatted with an initial blank line,
and this completely throws off the new parsing. While one may argue
that's something Paramiko should sort out, we're probably not doing the
right thing by having an initial newline.

This change simply gets rid of that newline, providing compatibility
with all versions of Paramiko.

Testing Done:
Unit tests pass on Paramiko 2.6 (pre-parser updates) and 2.7.0/2.7.1
(parser updates and parser fixes, respectively).

Reviewed at https://reviews.reviewboard.org/r/10864/

chipx86/reviewboard,reviewboard/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,reviewboard/reviewboard,chipx86/reviewboard