qa/tasks: a new cephadm exec task similar to vip.exec but generalized

Add a new cephadm.exec task that works similarly to the existing
vip.exec but instead of only considering VIP related string replacements
it uses that templating feature that was recently added to the
cephadm module for generalized string templating.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

qa/tasks/cephadm.py

@@ -1463,6 +1463,41 @@ def _shell_command(obj):
     raise ValueError(f'invalid command item: {obj!r}')
 
 
+def exec(ctx, config):
+    """
+    This is similar to the standard 'exec' task, but does template substitutions.
+
+    TODO: this should probably be moved out of cephadm.py as it's pretty generic.
+    """
+    assert isinstance(config, dict), "task exec got invalid config"
+
+    testdir = teuthology.get_testdir(ctx)
+
+    if 'all-roles' in config and len(config) == 1:
+        a = config['all-roles']
+        roles = teuthology.all_roles(ctx.cluster)
+        config = dict((id_, a) for id_ in roles if not id_.startswith('host.'))
+    elif 'all-hosts' in config and len(config) == 1:
+        a = config['all-hosts']
+        roles = teuthology.all_roles(ctx.cluster)
+        config = dict((id_, a) for id_ in roles if id_.startswith('host.'))
+
+    for role, ls in config.items():
+        (remote,) = ctx.cluster.only(role).remotes.keys()
+        log.info('Running commands on role %s host %s', role, remote.name)
+        for c in ls:
+            c.replace('$TESTDIR', testdir)
+            remote.run(
+                args=[
+                    'sudo',
+                    'TESTDIR={tdir}'.format(tdir=testdir),
+                    'bash',
+                    '-ex',
+                    '-c',
+                    _template_transform(ctx, config, c)],
+                )
+
+
 def apply(ctx, config):
     """
     Apply spec