mke2fs: do not use full path

At the moment, tempest assumes that mke2fs will reside at /usr/sbin.
This is not necessarily true, for which reason it's safer to just
avoid using the full path.

Change-Id: I6455bbc2e5cec14d2520b19fc00d183d02879e4b

tempest/common/utils/linux/remote_client.py

@@ -148,7 +148,7 @@ class RemoteClient(remote_client.RemoteClient):
         self.exec_command('sudo umount %s' % mount_path)
 
     def make_fs(self, dev_name, fs='ext4'):
-        cmd_mkfs = 'sudo /usr/sbin/mke2fs -t %s /dev/%s' % (fs, dev_name)
+        cmd_mkfs = 'sudo mke2fs -t %s /dev/%s' % (fs, dev_name)
         try:
             self.exec_command(cmd_mkfs)
         except tempest.lib.exceptions.SSHExecCommandFailed:

tempest/config.py

@@ -806,7 +806,7 @@ ValidationGroup = [
                default="password",
                help="Password used to authenticate to an instance."),
     cfg.StrOpt('ssh_shell_prologue',
-               default="set -eu -o pipefail; PATH=$$PATH:/sbin;",
+               default="set -eu -o pipefail; PATH=$$PATH:/sbin:/usr/sbin;",
                help="Shell fragments to use before executing a command "
                     "when sshing to a guest."),
     cfg.IntOpt('ping_size',

tempest/tests/common/utils/linux/test_remote_client.py

@@ -88,7 +88,7 @@ class TestRemoteClient(base.TestCase):
     # the information using gnu/linux tools.
 
     def _assert_exec_called_with(self, cmd):
-        cmd = "set -eu -o pipefail; PATH=$PATH:/sbin; " + cmd
+        cmd = "set -eu -o pipefail; PATH=$PATH:/sbin:/usr/sbin; " + cmd
         self.ssh_mock.mock.exec_command.assert_called_with(cmd)
 
     def test_get_disks(self):