Stop using not existing ShellCommandError exception class

In commit [1] was introduced exception class ShellCommandFailed
and it should be used in common.shell module. But by mistake
there was used not existing ShellCommandError class there.
This patch fixes that.

[1] https://review.opendev.org/#/c/612978/

Change-Id: I0b51165ea4d541b0cd2f5820a64cd7a82f23c6c9
2 files changed