Fix: lttng list -u <name> should only list UST

Fixes #654

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: report error if consumer can't be spawned

On error of the UST consumer execl(), we now exit the forked process
like the kernel does.

Furthermore, fix an error handling value when timing out when waiting
for the consumer to bootstrap thus returning an error to the client and
not continuing with the command thinking that the consumer was actually
spawned.

So, the expected behavior is to wait for the pthread condition and if a
timeout is seen, the client is informed thus making the client command
hang for the default timeout value of 30 seconds.

Fixes #702

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: don't start session if no channel

This adds a new error code that indicates that the session contains NO
channel.

Fixes #715

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: forbid session name creation if contains /

This adds a validation function for session name which for now denies
any session name containing '/'.

This is in response of bug #721 that actually uses a path as a session
name such as "test/../session1" which would then be concatenated to the
session path adding a relative path to it making this a serious security
issue.

Because of this issue, this is backported from master up to stable-2.3.

Fixes #721

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: flag that kernel streams FDs has been sent

Flag the session *after* every stream was successfully sent.

Fixes #731

Signed-off-by: David Goulet <dgoulet@efficios.com>