runner/resultgen: Added dynamically ignored dmesg messages

Some messages generated by driver are triggered by test itself
and are not meant to rise error nor warn within runner, yet
they should be catched in other circumstances so they are not
suitable to be ignored permanently.

Instead of hard-coding such situations check dmesg for info from
a test and add such regex on a fly and then ignore next dmesg
errors or warns which match it.

Ignored regex will be removed after end of current subtest, just
before a new subtest or dynamic subtest starts.

v2: removed local copy for regex string (Zbigniew), clarify
 description, free regex before creating new (Kamil)
v3: print error when compiling regex fails (Zbigniew)
v4: restore cutting regex string at \n, it was lost in v2
 (Kamil)

Signed-off-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>