Allow ironic to use ssh commands

Due to minor differences in the ssh command syntax between Nova-Baremetal
and Ironic, the regex on allowed commands failed for ironic. This patch
modifies the regex to allow for these differences.

Change-Id: I160e4202952b7551b855dc7d91784d6a184cb0ed
Closes-Bug: #1298731
Merge "Allow ironic to use ssh commands"